OK, if anyone is interested I finally found out what was making my 74
break-up under a load.
This is after I replaced the distributor, set timing, new plug wires, new gas and re-gapped plugs and also went over the Holley 700 cmp, dp.

The problem was a KINK in the 3/8 rubber gas line that comes from the fuel pump to the carb.
When the guy in the body shop put my engine back in he replaced the rubber gas line with a different type of rubber line.
Very soft and wound up with a kink in it.

**** happens.

A rubber hose on the pressure side is a bad idea. There's a good reason that it was a steel line originally. Recommend you replace it w/ a steel line or at least use the hose used on high pressure FI systems.

Corvettes and fire don't work well together. Glad you found the problem.