[DavidG]

It depends on how you define 'difference'. Apart from the differences between LHD and RHD frames, there were three distinctly different front cross members, three different center cross members, two different rear cross members, and three different sets of side rails (not counting the undocumented side rails without the ridge above the running boards). Some of those changes took place at the same time, so the net number of different frame configurations is at least six for LHD frames that I can document.