Sure grip pinion seal

I'll assume you're talking about an 8.75 rear and not a 7.25, since both were available with sure grip.
On the 8.75, it depends on whether you have a small pinion or large pinion carrier.
If it's a small pinion (casting #489 on the nose of the carrier) you will need a new crush sleeve in order to set proper preload. Follow the procedure in the FSM (you DO have one, right?). There is a crush sleeve eliminator available, but using that may require you to disassemble the carrier to install shims to achieve proper preload.
If it's a large pinion (casting #741, 742) just reassemble and tighten according to the FSM.
Use SAE 90W gear lubricant with a bottle of friction modifier for limited slip rear ends.