This looks good, too. I had initially been thinking more along the lines of the M1921's original cylindrical turret, but this is probably a better representation of what a conversion in 1932 would look like.
This gives a good idea of the size of the tank and the turret. The gun here is the original Hotchkiss 6-pdr, which was the same gun and mounting as on the British WWI heavy tanks. It was shoulder-stabilized and could be moved up and down as well as left and right inside the turret mantlet.
This is the tank, possibly the same vehicle, with a 75 mm M1920 pack howitzer in the same turret design. The barrel is on top and the recoil cylinder on the bottom. I don't know how this gun was mounted and aimed within the turret.
Like the difference between the British 18-pdr and 25-pdr guns, the US 3-inch M1902 gun and the 75 mm M116 howitzer had very similar but not identical shells.
- 75 x 272 mm with 87 mm rim, firing 6.8 kg shell at 380 m/s
- 76 x 273 mm with 88 mm rim, firing 6.8 kg shell at 518 m/s
My version of the M116 howitzer here uses the 3-inch case, which matches the existing stock of 3-inch field, mobile, and tank guns. I don't know if the difference in muzzle velocity was due exclusively to the shorter barrel (L/18 vs L/27) or due to reduced chamber pressure and a lighter loading.