JC Whitney has generic channel material that works perfectly in the painted sections. The chrome sections are narrower -- front on 2- and 4-doors, rear on 4-door -- and 140 rubber works fine there (mine came from a junker).

Originally there was brown wax paper-like stuff between the doors and upholstered panels. It's usually long gone by now, or decayed into uselessness. I got a roll of 4 mil plastic sheeting from the paint section at Home Depot (it's supposed to be used as a drop cloth) for a few $$$, and that's easily cut to size and stuck on with spray glue. One roll is plenty for several cars.