60-66 Trailer made from a 60-66 bed

[350TacoZilla]

Probably the safe way to figure would be to go off what the axle and springs are rated for. If you put a trailer axle under it with brakes the frame and suspension would have no problems with more weight, the functional trailer brakes is a big part of what I would feel safe hauling. We mainly used ours for landfill runs, home improvement store pickups, mowers etc like you would a small 5x8 trailer like I currently have so maybe 1ton upper limit? Though I'm sure there were a few times where we were pushing way past that with firewood in both the pickup and the trailer stacked up to the top of 2ft sides on beds.