No Stall?

A good converter for this package would be in the 2200-2400 range. Unless there is another problem with ignition or carburation then this should cure the problem. Does the problem exist only when you put in gear at idle? And then run fine once you get moving? If it does then the converter is a good place to look.
Can I ask you why you switched from an LD 340 manifold to a performer manifold? The LD is a good performing intake.