I'm not worried about folks adding info to my responses; I've got more time in service, outrank Gino and have more time in a TC's hatch in a wider variety of tanks than he does, but he's definitely the better modeler.
The 215th FSB (unit identified by the front bumper markings) was never equipped with that version of 5 ton tractor. The unit was originally the 502nd FSB supporting the 2nd Armor Division's Tiger Brigade until just after Desert Storm in 1991. The 502nd may have had 800 series trucks in the late 80s. By the time the 502nd reflagged and joined the 1st Cav as the 215th FSB (a newly created unit designation in 1991), they were fully equipped with M939A2 series 5 ton trucks (aka 'Bigfoot').
In 1994, I was pulled out of my tank company command at 1-12 Cav (kicking and screaming) to take command of the HQ Company of the 215th FSB. The Assistant Division Commander (Support) of the 1st Cav remembered my time as the 3-32 AR Battalion Maintenance Officer and knew that company needed help. He asked (told) me to go fix that unit.
Putting an armor officer into a support battalion to take command of one of their companies (thus stealing one of the few commands a logistics captain can have in a division) does not win you any popularity contests.
But, I do think your model is a beautiful build. I am very impressed with the workmanship. You just guessed wrong on the bumper markings, but that's no big deal.