My understanding is that cabs were/are the same between 40 and 47. They are also the same for 1/2 ton and commercial truck. Many '42-'47 pickups were scavenged for their cabs, for use on the 40-41.
The 38-39 cabs at first glance look the same too, but they are signficantly different.
My '46 has the gas filler on the passenger side. IF the 40-41 was on the DS, it wont make much difference whether or not it is used on the earlier or later 1/2 tons. Like above, pictures help.