So my employer wants me to restore this.

[motto]

The Hercules JXD engine is 320 Cu In displacement and weighs a little over 600 pounds. They were a fairly common power plant and were used in the Studebaker US6, White M3A1 Scout Car, M8 Ford Greyhound Armoured Car and Sperry search light generators to name a few applications.

Most parts are still available. The most problematic area would be the gear driven water pump which commonly had an exposed shaft with adjustable gland that is prone to leakage in the long term.
You will quite likely find that gearbox, transfer case and axles are not peculiar to the vehicle either. Identification is the trick. Being built for the military (assumably) there would have been a nomenclature plate identifying the vehicle and also an applicable publication plate listing relevant manuals and parts list attached in the cab somewhere.

You'd better ask the boss how much he is prepared to spend or how long he expects the job to take to get some idea of the level of restoration.

David