My 1940 1/2 ton pickup and my 1937 1/2 ton pickup both have the short dry element air filters without the silencer. The 37 air filter cannot be diassembled for servicing, but on the 40, the lid comes off to allow removing and cleaning of the mesh. On that filter unit, a NAPA 2373 paper cartridge fits very nicely. I'm not sure what your 37 air cleaner looks like, but my guess is that it has the tall silencer compartment below the dry filter mesh. There is currently a 1937 dry element air filter for sale on Ebay, and if yours looks like that one, I'm thinking that NAPA 2373 element might be just right. You might have to fit a slightly longer stud for the lid hold-down.
Mark