could be the coil, or MSD rusted inside.

sure sounds like a bad power valve did you get the gasket in tight??

got another to try.

I've seen the block to main body gaskets do the rich thing too.

Do you have a good running carb to borrow and swap on.

Do you still run the ballast resistor if so run a double male spade to join the wires.

you put fresh fuel in?