This is a really interesting discussion. One thing that wasn't mentioned was I believe the cabs with the external tank had a second inner panel of metal across the back. I blieve it was said that the tanks from a 52 didn't fit back there. I have an old factory photo of a cab being built and you can see the extra panel.
Also in one of my shop manuals from 1947/48 I have the instructions on converting the rad mount to two bolts and also adding ther cross bracing. This was a field modification to prevent cracking of the rad and some other structures. It also details crack repair procedures for some of the underside of the cab.
My 1951 Canadian 1 Ton had the single bolt rad mount.
