Rear wheel hub cover gasket that keeps the axle shaft in?
That's not a particularly hard working gasket and it's easy to get to so low risk in making your own.
I like to use premade gaskets whenever available but some gaskets are just as easy to make, this would be one of them.

If you're still searching for the new gasket at the auto parts store I believe the same rear hub gasket with 5 holes were used on the 10 lug (wheel) 3500HD (the model with I-beam front axle) with Dana 80 or Dana 70HD.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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