Hy YankyYank welcome, Thank you for making it possible for me to see your pictures. Your p.t.o. is in your driveline, so whatever it was driving the truck must be moving for it to work. I can see a lever which I presume is a clutch/shift lever for the p.t.o., the four belt pulley indicates whatever was being driven required a bit of horsepower to drive. Do you know anything of the history of the truck?