It has a Track & it Carries Stuff

[motto]

What you say makes some sense of things then Keith. As has been stated, the differential is certainly Chev pointing to GM involvement. Also GMHs choice of Lang Lang as the location for their proving ground post war may have been because of familiarity with the area. I don't know if they ended up owning the mud flats but suspect that part of the facility would be under-utilised if they did. Couldn't imagine a Commodore being put to the test.
For some reason the military chose Monageeta for their proving ground, no mud flats there to my knowledge.
It would seem that at this point in time the prime contractor for these vehicles remains unknown?

David