Dimensionally, all the frames are the same. However, the front half of the 4X4 models are different, as the 150 had coil springs and the others leaf springs. Also, note that while everything is dimentionally the same, the heavier duty trucks used a thicker gauge steel for the frame. As for out back, all used the same spring hardware, frame wise (shackles, etc.) except 2wd F-150s, which used 2.5" leafs vs. 3" leafs.