F500Mike - In regards to your question about the PTO. I just acquired a 56 F600 with a working hoist and grain bed. The PTO has a jack shaft from the transmission to the pump on the hoist to supply power to lift the dump bed.
Another lever then activates the pump to send the fluid to the lift cylinder.
So I am assuming your PTO would have supplied a dump bed or other option on your truck if so equipped. By the way, that is a very good looking truck too.