The best fix would be to machine a groove or two around the distributor housing for about a 3/32" O ring. The original HEI distributor used a gasket between the block and the distributor housing, but once that flange is machined or filed away, there's nothing to seal to with a gasket. A lathe cutter with the correct radius to fit an O ring would be pretty simple to fabricate.
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!
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