I've done this TWICE in a '91 idi, but the seal is the same as far as I know.
The first seal my friend bought from auto zone, and, not only did we have a hard time getting it installed properly since we decided to do it without removing the block plate.... but, the seal just didn't look as well made as the original, and well, it leaked!
SO, on the second try, we removed the block plate, popped out the new/old seal and carefully installed the new NAPA seal using some careful hammering and a block of wood.
When I do this again, I will relocate the seal slightly to keep it from running in the groove worn in the crankshaft by the original seal, or, I will use a shaft collar if one is available. You can knock the seal into the cover, but located it a 1/16" or so away from flush on the outside of the cover, keeping the seal from riding in the old groove. My friend did not like that idea, so, we put it flush with the front and it rode in the old groove and, well, it "SEAPS" just a little, not enough to cause a problem.
we rolled up a for sale sign greased it, then put it through the seal in the cover, and over the back of the crank, then, rotating and sliding the cover into place, the seal is kept from damage going over the crank, then, rotate and slide the sign out, and VIOLA! home made tool works GREAT!
I prefer gray permatex on all gasket surfaces after working in the honda engine plant in Ohio I'm sold on the stuff, I've had great luck with it, especially in tricky places like the front and back of a small block ford intake manifold... I don't use the rubber seals, they've sucked in on hard down shifts, nice bead of gray, NO LEAKS!
SO, that's what we used on the bottom of the block cover / oil pan interface. NO LEAKS
Sorry for writing a novel, good luck!