I am putting an S-10 frame under my 46 1/2 ton. It's a lot of work, engineering, and extra parts. Everything that connects to the frame has to be re-engineered, manufactured and fit. You have to figure out the bed height, cab height, distance from cab to radiator support, wheel base, ride height, exhuast system, fuel system, steering linkage, engine mounts, axle widths, wheel and tire clearances and etc.
I think you can see where I am going with this. You really need to have a full service shop.
Frank