IMO those paper diff gaskets are obsolete. Just squirt a bead of RTV around the cover, and be sure to make a circle of RTV around each bolt hole. Anything Permatex brand is a good bet.
They are not obsolete on an original truck.
And if you want something that will seal it an not leak, and its not as fussy about a film of oil like any silicon sealer is, use permatex no 2. I don't uses RTV much at all and never on an old original truck.
Why? Chevrolet didn't use it on them.
