I am a little late to the party of military trucks as loads...but attached are two photos from the Studebaker National Museum collection showing Studebaker US6 trucks at the South Bend plant loaded on railcars in 1942. Both photos include trucks loaded in P&LE gondolas. The yard photo shows 4 basic trucks, an open carload of beds/boxes, and many cars of K/D crated trucks.
This factory was served by PRR, NYC, Wabash (NJI&I), and (via IN) to GTW. At this time, Studebaker was still manufacturing open cabs, which the Soviets quickly asked to be eliminated in favor of fully-enclosed cabs. Nearly all of Studebaker's 6x6 truck production was delivered to the Soviets in WWII, as mentioned previously. 6x6 trucks of this era are straightforward to differentiate between builders: GMC CCKW had a slightly curved fender radius, Studebaker US6 were nearly right angles, and IHC M-5-6 trucks had a continuous long curve.