Pretty much what these guys said.
I start my end of season procedure with:
1: Change oil/filter & lube, check and fill all fluids including the gas tank.
2: Over inflate the tires by a few pounds.
3: Wash and dry car/coat of wax.
4: Vacuum/Clean interior/glass.
5: Place a sheet of thick plastic over the floor of the garage.
6: Elevate my car a few inches off the ground by means of some old Trex decking boards I drive up on.
7: Disconnect the battery in the vette. I don't trust old cars and their electrical systems. The GTO gets a trickle charger.
8: Loosened up the T-tops and leave the hood popped (not opened).
9: Place drier sheets through out the interior and engine compartment.
10: Place a container of Damp-Rid on the center armrest.
11: Put the car cover and forget about it until spring.
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GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44