Don't quote me, but I believe it is about 59... at least that what I figured my 1940 to be. I got an IMCA modified 9 inch for mine and spec'd 12 inch 6 lug disc brakes for the rear. I also spec'd the width to be 61" wheel to wheel.
There is about 11 inches of fender on the 40- 46 1/2 and 3/4 tons. The bed should be 48 1/2" wide. 61" in theory should center the wheels under the fenders if you are using a 7 inch wide rim with 4 inches of backspacing, or a 1 inch offset inward.
I plan to run either 245/70R16 or 255/70R16 tires on the rear of my 1940. I believe that the 255 (10.2" wide) tire will fit, but it will be tight. I HAVE NOT MOCKED ANY OF THIS UP TO SEE IF IT WILL ACTUALLY FIT. Take your own measurements, and do your own Math, as mine has been known to be a little bit off.
