I have seen the deal with the titles being dated when the truck was sold, before. Seemed to be a standard practice.
As far as the rear fenders are concerned, that story is a bit of BS, I believe. The "modern" rear fenders came out at the beginning of the 53 model year, so those rear fenders are from a 52. Oh yea, the 7 1/2' box IS the short box. They did have short or tall box sides for the 7 1/2' box. But hey, its been nearly 70 years since it left the factory, lots of legitimate reasons that may have a different box/rear fenders on it.
I'd drive the wheels off of it. Gene