Thanks, Bob! I'm going to guess that the flywheel flange on the GMC is larger than the seal area, right? Chevy 216-261 engines use a straight crank hub without an oversized flywheel mounting flange, which is why I can machine the back of the block for a lip seal like a late model Chevy V8, a Ford Powerstroke, and most of the Caterpillar Diesel engines use.
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!
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