How about the M3/M5 series of light tanks? They proved especially useful in the south Pacific in terrain that was difficult for larger vehicles. Reliability also endeared them to Commonwealth forces accustomed to maintenance issues with British tanks.

Ponderosa pine is not serotinous (needing fire or other disturbance to open its cones). It's rather poorly adapted to regrowth after a severe fire, since the a fire that can kill the trees is also likely to destroy its cones and seeds. Ponderosa is adapted to low- to moderate fire regimes.

That is correct.

I don't recall any of the T6 prototypes having a 6 pounder, but the counterweight in the photo resembles the configuration of some 75mm guns on the medium tank M3, so it's most likely a 75mm.

The bottom of the sponson on the Ram dipped below the side hatch, and the shape of the upper hull casting and turret were completely different. The Army determined the side hatch on the T6 represented an unnecessary weakness in the armor, so it was deleted before the M4 entered production