You're right, the '40 did not use the wide 5. It has the standard 5 1/2 inch bolt circle. I'm just learning about these vehicles. My '40 has the hole in the running board and the bracket on the frame for the '39 mount (and the indentation in the fender). The previous owner bought a new repro bed and painted it nicely. Problem is, he forgot to weld on the spare tire mount, so rather than mess up a nice new paint job, I am hoping I can make the '39 mount work. What do you think?