I think the best way to keep it from rusting is to sell it to me.... Of course I'm kidding, If the factory tar pads are not lifting at the edges, I would leave them. I know most will disagree with that but on the several cars that I have removed the stuff on, If it was still sealed well, the metal looked great under there.
Keep it clean and dry. If you have a leak at windshieldcowel like the Z's tend to do, get it fixed.
Inside the doors, make sure the drain holes are clear and all the dirtdust that holds moisture is cleaned out before you paint.
Other than that, the only thing I can think of is to keep it my garage.