Joe, with a Sawzall, a cutting torch, a MIG welder and a good hand grinder, anything will fit anything.
You're trying to envision this as a bolt-on kind of deal. Nothing could be further from the truth.
Find a body that you like. Think of the project in thirds. The front 1/3 is the front suspension and motor. The middle 1/3 is the body, transmission and controls. The rear 1/3 is the rear suspension and differential. Cut the middle 1/3 out of the frame and position the front 1/3 and rear 1/3 to the wheelbase that you want. Fabricate frame rails from 2 x 4 steel tubing and bolt them to the body with new rubber mounts. Position the middle 1/3 between the front and rear thirds and weld the whole mess together.
I know I'm just skimming across the top, but I have done this several times and found this procedure to work well.
If this makes no sense to you, then maybe this project is beyond your capabilities and you would be just as well off to part out what you have and use the money to help purchase something that is more complete.