You are not the only one in Liberty Hill that has a HMMWV, there is another member on here.
I lived in Liberty Hill in the late 60s, early 70s, we had a crank telephone system and was on a party line with several other folks.
The intersection of 29 and 183 was a 4 way stop sign and we had one blinking light in Liberty Hill
Yes on the listed 50A but common wisdom is not to pull more than 15-20A MAX. and even then only intermittently
Take care and disconnect the batteries every time you do electrical work and be VERY careful of polarity and the alt/reg will have no issues.
A couple other things, any time you are working on the truck where you are switching the run switch on and off disconnect the TSU (temp sending unit) for the glow plugs, it is the round connector with several wires attached on the passenger side of the water cross over on the front of the engine.
Otherwise under normal conditions EVERY time you turn the run switch to OFF, wait at least 90 seconds before switching to run again or you can fry the glow plugs.