While it might have been a USMC truck in the past, this M36 was most recently a US Air Force truck, based on the paperwork that you've found! The second load list that you posted shows the vehicle ID, and is corroborated with the very faint "68Kxxxx" on your front bumper. This is typical USAF registration number format, as described
in this thread.
In the top left corner of both the load lists, you'll also note the unit listed as: 148CCSQ...this was the 148th Combat Communications Squadron, which was stationed at the Ontario Air National Guard Station from 1984 through 1997. It looks like the 148th is still around, except now doing coolguy stuff at Vandenberg AFB.