...was hoping for an image but the link will do just fine.
This "M2A3" is a simple to build vehicle that can be used as a light Cavalry vehicle or APC. The image and the following links to others are all modifications of images made by the contributors over at Junior General.
http://www.juniorgeneral.org/load.php?Period=0
I agree about the 37mm ammunition as well, so I had another couple of thoughts.
http://joest2k.wetpaint.com/photo/11...+25mm+and+mk19
A M8 armored car with a 25mm cannon.
http://joest2k.wetpaint.com/photo/11...le+w+106mm+rcl
A M20 rigged with a .50cal and a 106mm rcl.
http://joest2k.wetpaint.com/photo/11514941/-
A larger APC based on the M3/M9 series of half-tracks but using wheels instead of tracks for easier maintenance.
http://joest2k.wetpaint.com/photo/11509388/m22a6+w+40mm
Someone else had the idea for using 40mm guns for ammunition availability...I had thought the same thing. This is a light tank based on the M22 Locust except with a 40mm gun.
The idea behind these rigs is the ability to improvise them from other types of vehicles, most being chassis for semi-trucks. Facilities for power generation, a foundry, and the mechanical equipment to build the armor, turrets, mounts and additional equipment. Using older armored vehicle plans and patterns ensures easier access to plans and technical drawings that would likely be unavailable for more modern vehicles. Another consideration is not using vehicles that are too large or too heavy to ensure that it wont take a ridiculous amount of time to build and/or convert each vehicle.