You've tried a different cam, you've tried a different carb, still same problem.

Have you tried a different distributor?

Have you verified with a timing light that your distributor is really doing what the guy who recurved it said it was supposed to? Did the guy who set up your vacuum advance distributor set it up for the fact that you would be disconnecting the vacuum advance?

Did you set the initial, then rev it up to see the what the total is at a certain RPM?

Here's a crazy idea that won't cost anything. How about just hooking back up the vacuum advance you said you disconnected and see what it does with it hooked up? It will cost nothing and take a few seconds.