there's quite a few good books on the history of GM trucks .... the 47 1st and 55 1st trucks were simply because GM wasn't ready with new models, for a variety of reasons including putting scarce resources into new car models first - after the war there were problems with retooling, material shortages and particularly labor strikes, closing GM plants from late '45 until mid '46 .... note that new models back then were introduced after Oct each year and production needed to be set up mid year .... in 54/5 the Korean war contributed to some of the same problems, and the 55 2nd wasn't ready to roll until early 55, so something had to be sold after Oct 54 as a "55"
nothing to do with using up leftovers, GM has always been king of using parts designed in the past for it's current vehicles, back then there wasn't totally new designs every year
Bill
