could be lsd, or it could be bound up in such a way that it acts like it is.
the H190 did come as a lsd or an open unit, so it is very possable that it really is one.

why not just change the whole handle assembly? as I recall the button is molded to the rod and can't be removed without breaking it. it shouldn't take more than 1/2 hour to swap them.

the 240Z had the R160 diff. this is an IRS unit, not even the same thing. you can put Z car drum brakes on it but your right you will need to use 14 inch wheels. an alternative is out there, I just am not that familiar with what was sold down under. check out the 80-81 Silvia/200SX model S110, don't know about there but here in usa they came with a rear disk brake setup that will virtually bolt up. I'm just not sure that you will be able to run 13 inch wheels with them.

unfortunatly, the answer is that only 1200 parts will fit with out major work.
check your local body shops for one that has the capability to straighten unibody vehicles.
what this entails is clamping the body down at the rocker panel pinch welds and using a hydralic ram to pull things back into shape. unless there is real major damage, an experianced shop should be able to repair what you have, how much it will cost will depend on them.
good luck

disagreement??????
difference of opion is the way I see it. what works for you may not work for me, and vise-versa. you base your opinion on years of experiance, and so do I, nothing more to it, other than that.
following the manufafturers recomendations is the only way to go, but even they (manufacturers) change their recomendations from time to time, it's wise to check.

this is long, but please bear with it, it will make sense.
Mareo this is not personal, so lighten up a little will ya? you are frustrated with a problem you can't figure out, so you asked those who are here for help, but it seems that you don't like the answers you are getting, WHY?
first off you are using the wrong plugs, please get a second opinion to confirm this, Nissan specified BP5ES for the A series with point ignition, BPR5ES-II for electronic ignition. BP5EY is for toyota's and honda's NOT NISSAN, again I beg you to have someone else confirn this.
despite how it might appear, I DO NOT claim to know everything, no one does, we all make mistakes, me, you, everyone.
stop and think about a few things, then go back to the basics. a restrictor plate works great for a race car, but isn't very practical for the street, why? very simple a thermostat is there to regulate engine heat, as in keeping warm water in the motor until it reaches normal operating tempurature, after the motor warms up, it also controlls the flow of coolant TO PREVENT OVERHEATING. if the coolant does not spend enough time in the radiator to allow it to exchange heat and cool off, IT WILL CAUSE AN OVERHEATING PROBLEM., go buy yourself a 160 degree thermostat and a new gasket and put them into the car and run it, maybe it will help, maybe it won't, but it can't hurt to try, at least you will know for sure that this is not the problem. with as big as radiator as you say you have you should never have a cooling problem.
you say you tried water pumps, radiators, flushes, etc., etc. and didn't get results. the only other thing besides the carb you haven't changed is that restrictor plate, or so you said, could that be the problem?
again, NOTHING PERSONAL, we are all here to help each other, not get into pissing contests. I've doing this for the better part of 30 years, and have seen a bunch of things cause problems like you are experiancing, problem is that I don't know you, your background or you car so I do need to cover all the seemingly stupid possabilities just to make sure. I could be way off in the ozone on this, but please think about it.
in re-reading your last post, I have a few questions, what motor (as in A12, A14)?
what compression ratio are the pistons? (stock dished, flat tops, domed) which cylinder head (casting number H10, H23, H62, H72, etc.) has it been bored?, with or without a heater (yes this could make a difference) what cam? is it possable that the cam timing is a tooth off? (see this all the time on belt driven motors) I ask that one because you say the timing is set at TDC and you still get ping, could be that the cam is advanced 1 tooth and causing the problem. I have ran A12's at 25 degrees advance flat out hard on pump gas and never had a pinging problem.
it sounds as if you have covered most of the obvious stuff, might be that you are going to have to start taking things apart and verifying that the mechanicals are where they need to be. if that isn't it and the motor has been bored, could be that the cylinder walls are too thin, this would have been caused by core shift in the block casting.
good luck.

Mareo,
a cupple of thoughts about you problem,
the following things are what I have seen that has caused similar problems;
check the water pump impeller and make sure that it is attached to the shaft, I know it sounds crazy but I have seen them come loose and look ok, and still be slipping as they rotate. make sure that the impeller is still there, I have seen aftermarket waterpumps that had stamped steel impellers that litterally rusted off the shaft and couldn't circulate the coolant propperly.
back in 75 Nissan came out with a heavy duty water pump for A/C equiped cars, it has a much better impeller design and eliminated similar problems on A/C equiped B120's the old part number was
21010-H7226, it has probably changed part numbers by now, it will have a larger hub for mounting the pulley so you will need to get a different one, you said that you have access to a salvage yard, look for one with a fan clutch, that's the heavy duty setup. if you can get one, you don't necessarily need to use the fan clutch, you can get a universal fits-all fan and put on it.
the other things that will cause a problem like you have are a carb that is too lean or spark plugs that are too hot in the heat range, or possably both. it might be a good idea to get a new set of plugs that are the correct heat range, go to your favorite autoparts store and ask for NGK BP5ES, that again is an old part number, but they should be able to cross it, either that or go to your local dealer and get some, they shouldn't cost you any more at the dealer.
also, if you are in serious need of a good carb, contact me off list, I have a line on something that might help.

make sure that the vacuum advance hose is attached to the fitting at the center body of the carb. this will give you ported vacuum and cause the advance to only be there when the rpm's are above idle, if it is hooked up to manifold vacuum, it will have advance all of the time and it will affect your performance. the way to tell is when it is idleing, take the hose off at the distributor and put your finger on the end of it, if you can feel it sucking, it's hooked up wrong.
when you set the timing, disconect and plug the vacuum hose at the distributor, that way you set it with only initial advance. and like I suggested before, set the timing at 10 degrees, it will run better still and shouldn't cause it to ping.

so you know, the 71 1200 did not have EGR, if you are refering to that pipe at the left rear of the block that is about an inch round and a hose going to the intake manifold, it is the PCV system.
the PCV system and a primitive vapor recovery system are all the emission controlls that they used on 71 to 73 USA models.

it almost sounds as if you need to go back to the basics.
first pull and check the gap on the plugs, spec is 0.030-0.035, it's best if you set them at 0.030 as they will wear to a larger gap. then set the points (this is assuming that you are running a point type distributor) use a dwell meter if at all possable, it is much more accurate, dwell spec is 49 to 55 degrees, again try to get it set to the lower figure. after you have set the points then set the timing, I always ran mine at 15 degrees (second mark) because of altitude, you might be best off setting yours at 10 dergrees (center mark) only set the timing after the points are set, the reason for this is that for every 1 degree of change in dwell, the timing will change 2 degrees and this will affect the way that it runs.
good luck

there are actually 2 different screws, 1 to set the mixture with, and the other to set the idle speed with. you found the mixture screw, the speed screw is the one on the side to the rear as I remember with a spring arround it too. some call this one a throttle stop screw. adjust this one to raise your idle speed, and then adjust your mixture screw for the best idle smothness. once you have raised the speed, you should be able to turn the mixture screw in more and get things where you want them.
remember that as the speed screw is turned in (clockwise) the idle speed will increase, if you have a tach. set it at about 750 to 800 rpm, THEN adjust the mixture screw.