Our first camper was a 67 Ford Ranchero that I made bows for the bed out of electrical conduit and we threw a tarp over it and straped it down with bungies. Rolled out a foam mattress and threw some sleeping bags on top. Used it for a couple of years then bought a camper van that had been wrecked. Body was repaired but the interior camper mods were mostly destroyed so it was gutted and I built a minalize camper inside the van shell. It had a popup top so it was a comfie upgrade and we used it for years before graduating to our first slide in popup camper.
