The general rule of thumb for drum oversize is a maximum diameter of .060" oversize passenger car drums, or .090" over for pickups. It wouldn't surprise me if your 70-something year old drums are somewhat bigger than that.
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!