My answer would be the weakest link in the chain determines how much I can pull. But since I don't know what the frame is good for, I can't evaluate that part. I can buy a hitch with the rating I need, I can use axles with known rating, but how do I know that my 1-ton frame will handle the load.
I agree.
About the frame, I would start with the factory recommendation for the truck original to the frame. From there I would evaluate how the hitch mounts and transfers the load to the springs. It's mostly a guess, although I suppose you could get out your structural engineering handbook and get very technical, add a factor of safety and it's still a guess, but closer.
The seat of the pants test on how it handles and how effective the brakes are will probably be the deciding factor, assuming you see no obvious mechanical weaknesses.
Grigg
