99 problems and a Ford ain't one.

I agree 100% with stepping back and taking a breath. I also think you should diagnose what you "have".....let me explain.

First let me start by saying don't take any of this personally, as we ALL have our limitations and we all need help sometimes. I've had things slam kick my BUTT over the years and had to reach out to others. Sometimes it just happens.........but and this is the part not to take personally. ........if you cannot get this 340 running right, what makes you think you can get a 383 running right "just because" that's what the car "came with"?

Maybe we have a member in your area that could lend a hand? I would be willing to talk to you on the phone about it. If it ends up being something about the CAR rather than the engine, what will you have done swapping a 383 in it? Nothing. Not a darn thing. What if it's trash in the fuel system? No engine you put in there will ever run right. Rather than throwing parts at it, engine included, take a break, take some deep breaths maybe for several days and then try some real diagnosis. Lots of people think diagnosis is throwing parts at something until it's fixed. That's not it. Real diagnosis is collecting data from either testing or process of elimination. Seems most people are too impatient for that nowadays. Send me a PM if I can help. I'll be glad to.