What brand of distributor are you using? If it's one of the ones being sold on Ebay, it's made in Asia somewhere, and they're notorious for the electronics failing quickly. Why not use the original equipment GM electronic ignition with the coil in the distributor cap? It's a close fit to the firewall, but it will usually work with little, if any reshaping of the sheet metal near the cap. Does your small-cap distributor have a vacuum advance? I'm not aware of one that is made for a small block V8 that doesn't require an electronic timing control computer.
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
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