I would start bu not calling it a "CAR". I think that some of the Jeepers here may want to
Remove the back seat, carpet, and top. Have the entire belly pan (floor board) from the front to the tail gate rhino lined or line-x'd. This will stop it from rusting. Slap some big phat tires on it and haul some........ well you know.
Wish my wife had bought me a Jeep when I came home from Iraq. AWESOME!!!!