I'm working on a 40 1/2 ton and decided to get a parts truck.
I bought a MIG welder and am reworking the fenders. I figured the welder would be cheaper than the cost of good fenders.
I don't know where you're located but there are several 40s around that you could use as parts.
The floorboards are tough to find, I'm using a fiberglass one until I can locate an original. Beware that the floorboards aren't the same for all 40 trucks.
All depends on how much time you have.