See http://www.nastyz28.com/forum/showthread.php?t=99672
Something may twig your mind on this that the Camaro guys overlooked.

replace the distributor with a new hei unit there dirt cheap and run great

also you could have a bad aftermarket ignition ...if you have a msd or anything else bypass it and run the stock ignition

only other thought is change all plugs and wires

this is a long shot but timign chain problem would casue it not to rev if it skipped a tooth but that unlikely

put and hei in it

Fought one like this years ago ,turned out to be bad cap.

Thx guys, it's got the original points type system from 1970. I think the HEI would be too wide for my original breather. It's tight with the open element and mine has the dual snokel which are even closer to the dist.