I'm guessing that you have an L16, the correct plug should be BP6ES. But what I see is a lot of black around the edges, indicates to me that you re running rich, leaning out the fuel system might be more helpful.

Judging from your pictures, your carb. is filthy. IF loosening the pilot is the only way that it will run, then the carb is dirty on the inside and needs to be cleaned. Be very careful when disassembling and write down what comes out of which hole, so that you can get the jets back into the exact same hole they came out of. It's not hard to do, it just takes patience. The only adjustable screws are the ones in the first pic, the idle stop, and the the idle mixture screws

First, welcome, you will find that this site has members from all over the world.
I have some questions, Does the fuel filter look clean or is there dirt inside? If I understand your post, you are still running a points type distributor, is this correct? Are you still running the coil resistor, or have you removed it? (the white ceramic block) When you reassembled the carb, did you put the jets back into the same place they came out of? I ask this one because they will fit into the same holes, but the holes in the middle are different sizes, easy mistake to make. What do you have the timing set at? should be set at 20 deg. The points should be set at 49 to 55 deg. dwell, or 0.028 to 0.031 in. gap. (about 0.75 mm) The spark plugs should be set at 0.032 to 0.035 in. (0.75 to 0.78 mm)
For what it's worth it sounds like you are running an electronic ignition coil with points, doesn't work too well because the coil overheats and goes flakey. If this is the case, go back to the original style coil with the ballist resistor, and it should help your problem go away. Points systems are designed to run on 9 volts, which is why they have the resistor. Hope that this helps.

Actually it was available in the U.S. as a dealer installed option.
I remember the guys in the shop complaining about how difficult they
were to install and make them look good.

Late 1970's USA production cars, produced by Datsun comp. in Compton Ca.
You could have your favorite dealer order them for you, cost like $8 each
if I remember correctly. I never sold any because most people thought them
too expensive.

Too bad you won't be here late august through early september. Then you could stop at the Bonniville salt flat durring speed week and see all of those trying for land speed records. As far as older Datsuns, I hate to bust your bubble, there aren't that many left unfurtunatly. It's kinda sad that all there is for sale any more are old Z cars for more than they cost new. anyway good luck in your trip and welcome.

NO!
there isn't enough room between the firewall and the core support for an inline 6 to fit. I own a 720, my solution was to put a VG30 into it. Not a bad fit, but I had to build a custom oilpan to clear the front diff. I haven't said anything about it because this is a 1200 forum.

if you have fuel and you have spark, try adjusting the valves. more often than not, as the engine runs the valve clearance gets tighter, eventually causing the valves to actually stay partially open, this would explain the backfire and rough running.
because the engine is cold, set the adjustment at 0.012 in, until it is warmed up and then readjust them to 0.014 in. when hot.

try gt-racecar.com, there is a lot of information there also look in the members section for Peter Zekert he lives in St. Louis and is one of the best resources arround

pnc 96301 = right hand mirror and 96302 = left hand mirror many times one had to look between the lines to find the listing, also a lot of times things wern't actually shown in the catalog but listed in the price book. a good parts man understands this and knows where to find what is not always in shown