Frank suggested the following, “a suggestion, which I have done myself, is anyone who may be building a Jeep with a new metal body try sealing all the seams where the floor or rear fenders contact the body with urethane sealer (in the caulking tube). It’s about $10 or $15 a tube as I recall. Just make sure that all the surfaces you apply it to are clean and dry.

Since the main reason Jeeps rust (I believe) are all the seams and crevices that hold water, sealing out the water should help. Urethane is also sandable and paintable. It is used for installing windshields on late model cars and trucks which makes the glass an integral and structual part of the body in an accident.”