I think you'll be better off buying modern rims that mimic the appearance of the original wheels. Finding a decent set of 80 year old wheels will not be easy and you'll have to pay a decent bit of money to have them restored, straightened, etc. 16" is most likely the factory size. That is what my '50 came with and I think 15" looks too small under the fat fenders.
I purchased a set from Wheelsmith, which custom builds the wheels to order. Mine are 16x6 with 6 lugs and 3.5" backspace. If I were doing it again, I'd order 16"x5" to more closely resemble the original 16"x3.5" rims the truck came with. They'll build the smoothies to the same specs as your originals.
Wheelsmith will supply reproduction hubcaps or will install the clips required to use your original caps.
Here are some photos of mine.
225/85- R16 is the closest modern radial size to the original bias ply tires.
http://thewheelsmith.net/wheel-catalog/smoothie-wheels
