From the picture of the ip/governor looks to be different then the wrecker governor, according to my cummins PT fuel system tm, the governor looks to be a variable speed governor that is normally used to meet the requirements of machinery on which the engine must operate at a constant speed but where extremely close regulation is not necessary, this is normally used on a stationary power plant, It looks like the military used the standard ip with the maximum speed governor and added this governor to it as a auxiliary governor for the generator in the back.
The reason I did not post up on the truck use and set up question is because my cummins book only talks about adjustment for a stationary setup, I am pretty sure adjusting this for the truck would not be to bad, just configure the truck as a stationary setup for the purpose of running the rear equipment