I might have some service manuals that cover governors in general, but maybe not that specific one. Those Firestone RH-5 "widowmaker" wheels will need to be swapped for something safer before you put the rig on the road. They lock together with a tiny lip in the center of the wheel, and they're notorious for separating as the tire is being inflated. The wheels aren't simply dangerous, it's also illegal for tire shops to service them. If those rear hubs have 10 lug bolts, I need a couple of wheel centers (not the complete wheels) to use for a tractor project I'm working on, so please consider sending me a private message before you scrap them. Thanks!
Jerry