Aha, I figured it out, when I got the truck, I hooked the battery cables up how they were made in the truck. The battery cables looked new, but it wouldnt turn over, so I replaced em. Well, bad move, because the cables were in the truck wrong, the feed to the cab was off the positive side of the 2nd battery. Basically the cab was getting 24v so yeh, hopefully nothing else is fried.
Im actually hoping the burned up FSS was the reason the Marines parked it.