The 1 ton beds are as rare as a hen's teeth. Especially ones that are in good shape. Quite simply, GM didn't make alot of the 3804 trucks. Most 1 tons were destined for flat beds, stake sides, etc...
The 3/4 ton beds are more plentiful, but still a little rare.
If you wanted to do some fab work, you could always shorten your frame and move the rear axle forward. Of course, that would entail a ton of work. Shortening running boards, shortening drive shaft, brake lines, etc...