They even made some of that body style in '47, using up parts. A 4bt will be a tight fit, especially with an I'cooler. A 6bt will not fit without extensive mods. That might change the look of the truck.
Ed
I haven't done any measurements or research on a 4BT vs. 6BT so it's TBD. I did see a guy who put a 6BT in a 1/2 ton early 40's truck. He had to move the radiator fwd a little bit but no firewall mods were needed.
