Eric, the bed on my 41 1/2 ton is 79 1/2 x 48 1/2. You could also try a different wheel with more offset to get the tires back under the fenders. On resto packs sometimes you have to talk to several people to get the info that you want but the tech info is worth the trouble. It is an 800 # and the cost is free so spending a little time on the phone is a minor inconvenance.
Here is is site that has most of the resto infor posted for the 41-46 and the beds are the same.
www.brads41-46chevys.com
