I believe the GMC crankshaft has a flywheel flange that prevents a full circle seal from being installed in the proper location. The stovebolt crank has a straight flange that allows a lip seal to slip over the flywheel mounting bolt circle and contact the seal area. The same type of seal setup is used on the late model small block Chevy V8, beginning in the early 1990s, IIRC. Ditto for Ford Diesels, and Caterpillar V8 Diesel engines.

Confirmed- - - -check out the flywheel flange on this GMC 270 boat anchor listed on Ebay:

www.ebay.com/itm/372199684453?

235 crankshaft- - - -the lip seal rides on the 3 7/8" diameter surface at the very back of the crank:

www.ebay.com/itm/315239781392?



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!