[hatzie]

I'm not a fan of the AutoZone or National Chinese bearings. Eastern Europe is just as good as USA made and I'd take Japan, Korea, and Taiwan sourced bearings over those made in mainland China or India. FAG and some SKF bearings are still made outside of China and India... and some Timken taper bearings are still made in the USA or they are old stock.
I just bought six Timken SET6 bearing sets for the tine shafts on three Troy Bilt Horse I tillers and one Horse III tiller that I'm rebuilding along with ten Timken SET2 for the main shafts and eight sets of FAG 6201 bearings etched Poland. The Timken bearings are all etched USA and they cost around $8 each.

The parts guy at AutoZone couldn't find the proper grease seal? It's a separate part.

The GM part number for the grease seal on the 1974 GMC RWD front brakes should be 3857731 if the GM parts books are to be believed.
AC Delco lists 290269 for LD front brake rotor grease seal. That doesn't cross to the GM part number in the 73-78 parts books... It's possible I looked it up incorrectly but it lists 73-78 CP- 2,3, M.H.C and CP-1 on page 943 of the parts book.