Back when these engines were daily drivers, if a journeyman mechanic couldn't install a rear main seal before lunch with the engine in the car, he would find himself unemployed. Doing anything short of a major overhaul was always done in the frame back when I learned this trade. I've even seen cylinders bored and crankshaft rod journals reground without pulling an engine. Sometimes I'd dig into an engine and find ONE oversized piston, and/or one undersized rod journal after that kind of work!
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!