A few pics and comments...

Here's a few pics of the Beast. 1975 (according to the registration). It was a communications vehicle and think would be a M882...? I'm going to try to get it polished up and make it my primary plow vehicle. The parts vehicle below had an older Boss plow that someone messed up a bit. Welded the blade straight, welded the plow frame to the truck frame, etc.... It was a lot rougher than the camoed truck anyway... Enjoy.

Nice looking truck...I love that older 4-color camo when it is clean!

WOW!
It is rare to find the 24v system in place in these trucks!
Speedo has been replaced, the originals did not have kilometers.
Data tag on dash?
an M882 would have antenna mount holes in 3 locations on the bed sides, (bed could have been changed though)
as for the year, sometimes government employees are a bit tunnel visioned, It was probably built in 75 but would be a 76 model year, check the VIN, 6th digit is the model year.
Seat bottom has been recovered, floor pans look good!
Back window looks a bit thin............

What is the vise grip holding under the hood near the master cylinder? I also noticed that the alt gauge looks funny. Check it out. A lot of them have taken out the instrument clusters as they were not shunted and all the electrical system runs through the gauge and the cluster. That is except for your 24 volt alt and the starter.

Yeah, the back window is a bit thin, but is the clearest I've ever seen...lol The part's truck will be making a donation there. What is odd about the Alt gauge? Is this the gauge that is infamous for frying the whole cluster? I like alt meters. Is there a fail safe way to wire it in to avoid the problems they have caused in the past?

The visegrip is just holding a bit of scrap wire to the starter relay. I was using it to short across the battery to turn it over when I was working on the fuel pump and first trying to get it running. Suppose I should remove it now....

The gauge looks like it is mounted to high or is loose. You should be able to see the d and the c on the meter. It may be the angle of the pic but compared the other gauges it looks off. As to how to fix it. I don't know other than keeping an eye on it. Someone else may be able to tell you how to make a shunt. I don't know that much about it other than seeing a few fried first hand.