i recently aquired a 71 1200 coupe with a A12, extractors, straight through exhaust and a celica 5 speed. I have a steel 6 point cage to put in it when i get some other stuff sorted. Okay the stuff i need sorting. The carbies float bowl is warped so im told so a new carby is needed, should i put a standard one back on or what else will easily fit. The front has been lowered but it seems to be quite dodgy cause it raises the car on full lock? and makes rattly noises. I havent had a chance to get under to have a look yet but give me some ideas of what to look for.Oh yeah it supposedly has a 1200 diff in it but im not sure is there any diff replacement thatll lower the revs when cruising at 110kph (currently 3800rpm)
Any info would be great and i look forward to surprising a few cars with my lil beast

I, personally, wouldn't replace the carb with another stock one. I'd try to find a Weber 32/36 DGV series carb and the little adapter plate. Redline used to make a kit but I'm not sure if they do anymore.
As for the ring and pinion gears to slow the engine down, I'm afeared you're out of luck with the 1200 differential. The only R&P ratio that Nismo lists in the latest catalog is the stock 3.9 ratio. If you were to swap in an H-150 axle from a B-210, there are a few more options, 3.7 and 3.545 for instance.
The problem with the front suspansion may be that the tires are hitting the fenders, or guards, or wings, or whatever they are called wherever you are. Look at the front of the opening while someone turns the wheel lock ot lock. If it hits, there's your problem. Also, the tire might be hitting the inner fender. turn the wheels all the way and look inside. If the paint and undercoating have been rubbed off, that is the problem. Fixing these is a matter of clearancing the fender for the first problem and adjusting the steering stop for the second. Of course you could get narrower tires too. What size tire are you running?
That seems to answer your questions. Enjoy your new toy!