Here's the deal. This is the second time I have rebuilt this engine. The first time I had alot of fuel problems right up until it spun a rod bearing due to machine work that was off. I actually spotted the machine work being off after plastigauging it and I brought it back to the machine shop to have them check it and they said it was ok. The next mistake was my fault, because instead of bringing it somewhere else for a second opinion, I just put it back together. $500 mistake.
Since the second rebuild (last week) I replaced the original computer controlled distributor (no computer on the vehicle) with a vaccuum advance one. Before spinning the rod, I was constantly fouling plugs with the new carb, and I went 3 stages lean on the mixture and it was still fouling them. Since I have put it back together, the old plugs have all turned white (like they are supposed to be) from the black that they were before. I know I should have probably used new plugs, but the old ones only had about 6 runs on them before the bearing spun.
I had a similar problem before the bearing spun if I remember correctly (it was about a year ago now) with a rough idle on startup. To answer your question it is manual choke that is turned completely off when giving it gas to keep it running and it sounds like it has a mean cam in it until it warms up. I really suspect it to be a carb problem, but the carb is brand new out of the box. I am running the recommended 5psi fuel pressure regulated from a holley regulator and supplied by a holley blue pump. By the way the carb jets are still 3 stages lean which I could probably increase some although I am not getting any detonation under a load (it does seem to lack power though). I think this is my whole story, but if I left something out - Just Ask!