Maybe someone will give you a measurement of the width of the radiator bracket. Then you can at least have an idea what width you need. My Motors Manual doesn’t give the measurements for the bracket. It does show the 327 in a bus takes 18 1/2 quarts to fill. I measured my 1/2 ton and it is 21 1/2 inches wide, I’m sure yours would be much wider. Good luck on your quest.
I think I have found one locally. The guy sent me pictures of it and he said he is pretty sure he took it out of a Chevrolet C-50 with a 283 V8 engine. He said his had a plastic fan shroud, which mine does too. He will allow me to take it and try it and if it fits, and is good I can purchase it for $50.00. If it is not good or if it doesn't fit I can return it to him. I'm going to take him up on the offer and see what happens. Even if it fits and leaks, maybe it will hold water good enough to run the engine some. Look at the pictures and tell me what yall think.......if it should fit or be the correct radiator. Looks like its definitely leaked and had some repair in the past.