Use a donor HEI from a 250 or a 292. Grind the shoulder off the housing so it can drop about 1/4" deeper into the stovebolt block and transfer the pinch clamp off a stovebolt distributor (after removing the vacuum chamber) to hold it into the block. The extra depth is to assure that the oil pump drive gets engaged properly. It's been done that way for decades.
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!