Try going back to a point-type distributor for diagnosis purposes, or at least an OEM electronic distributor. Those aftermarket HEI's are made somewhere overseas, and they're about as reliable as a promise made by a politician or a used car salesman. At the very least, put a Delco Remy original equipment module in the new dizzy.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!