That doesn't look small enough to be a 37 to me. A 37 would not need five men (even in mud) to move it.
Sgt, Scouts Out!
look at the single photo that I posted, which is two photos cropped together as one for ease of posting. Garys' description of the two weapons was correct. I merely posted that picture to show that the designated personnel carrier, the M3/M3A1 was often used in the prime mover role even though the M2/M2A1, which had large stowage bins up front to hold the ammunition of the weapon it would tow would seem to make more sense.
Build how you like, like how you build.