First thing I'd do is spray inside the chassis rails, bulk head and any crevices you can get access to with some sort of rust protection. I used to use lanolin until my neighbour who is a panel beater sprayed the whole thing with a thick wax like product that drys to a firm skin. This skin is firm and flexible at the same time and doesn't Crack. He uses it in his hot rods etc so it must be good.

