I use Fluid Film. Stays on the metal better than WD40 which is too "thin". But it really depends on how long it's gonna sit. Couple days to a week, WD is OK. Up to a year, Fluid Film. Over a year, pack in cosmoline and bag it.
My 320 had a 3.889 roadster differential, a 200SX dog leg 5 speed, and a J16 engine with a Weber carb and header. I could drive mine on the freeway with ease. The only problem with that is that is also had stock brakes.