I'll be running 255/70R16s in the back of my 1940 GMC, and 235/70R16s in the front. I will be using 6 lug artillery wheels that have been widened to 7 inches with 4 inches of backspacing. My custom rear axle is 61 inches wheel mount to wheel mount (2 inches wider than stock), and all the math says it will just fit under those rear fenders. I don't know yet because I haven't got my rims back yet, and I don't have the stepside bed on my truck right now.
Good Luck!
John
