It's not impossible to find a "rebuildable core" on Ebay. Anything from the late 1950's to late 60's, 283, 307, or 327 would probably be in the ballpark, calibration-wise.
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!