Hi, I have my 88 F250 xl superab longbox 4x4 ZF5speed over 8,800 gvwr, so I think it is a heavyduty, 10.25 ford rear tbb dana 50 front, 3.55 gearing, truck got 20mpg on highway at 1,700 to 2,000 rpm, some rust along the very bottom of the cab but truck is 90% rust free, frame has no flaking...