look for a rear tank from an f-superduty, I think they started in 88, and went up till 97, they have the same rear tank size as the super camper special. Also share the same skid plate. You can also use a rear tank from a f-350 cab and chassis dually up to 97, they share the narrow frame with the crewcabs, highboys, and f-350 camper/super camper specials. The f-350's also have the crossember that will bolt into the older trucks to add this tank, and the same skidplate as the f-superduty. the f-superduty crossmember is to wide to use. The filler neck is a little different, and I look for the earlier tanks with the idi diesels as they don't have a pump in the tank.

These poly tanks bolt right in and fit with no mods, mabye drill a few holes in the frame for the crossmember if you did'nt have a rear tank in your tuck. My buddy has this tank in his 78 f-350 he is restoring, and I put one in my 75 f-250 4x4 i'm restoring.