You guys are great! I got busy for a few days and came back to the thread, and look at all these ideas and links. Thanks! Basically this is exactly what I'm talking about. The Jim Carter '46 shows the top side rails of the bed (not sure what the proper term is) wider than the cab... a widened 3800 bed on a 4100 chassis would have that approximate bed/cab relationship. And the tubs for the inside wheels would work just like the '57 that jfnar linked.
Hmmm...
