Originally Posted by Hotrod Lincoln
I'm working on a similar idea. The 2 piece seal for a Chrysler 440 engine is pretty close to the diameter of the GMC seal surface. I'm considering milling a flat area on the back of the GMC block and rear main bearing cap, and making a seal holder from aluminum that will occupy the same area as the rope seal does now, then grind the crankshaft to the correct diameter for the seal. The seal holder would attach with flat head screws.
Jerry

I purchased 2 Garlock seals, not being sure which I'd end up using.
1) #25003-0806 3.560 OD x 2.812 ID x .375 thick
2) #25003-1039 3.740 OD x 2.835 ID x .375 thick

Looks like either one will work. The advantage of these seals is that they don't require a seal adapter. The OD size is larger than the original seal groove so the original groove can be machined away and the seal fit directly in the block. It will require seal retainers since the seal is open to the rear and the seal will have to be on the crank when it's set in the block.
It appears the Chrysler 440 crank has a 2.81 dia. seal surface on the crank. If I use the seal with the 2.812 ID, and it doesn't seal properly, I could make a seal adapter and use the Chrysler seal. It would require an engine tear-down though.

Just occurred to me that my seal retainers will have to be screwed fast after the crank is in place, leaving no room for an allen wrench between the block and flywheel flange.
I'll have to make sure the screws for the retainers line up with the flywheel bolt holes well enough to get the screws in through the flywheel flange.