Well, I went to look at another parts truck yesterday a little more than 2 hours from home. From what I could see (could not get inside due to frozen door latches) it is a 1960 F750. I made a deal on what I want, but there are several interesting things on this truck - power steering and air brakes. It also has a 2 speed rear. Mechanical parts look good, but there is not much left of the body due to rust. If anyone wants info on this, PM me. From what I have seen, power steering was not too common on these, and I do not know if it can be adapted to the F500 and F600 trucks.
Speaking of power steering, my '60 F100 has the steering box and column out of a '59 F500. The box itself is perhaps twenty percent bigger than that of the F100. With the total rebuild of the front end and the mechanical advantage of larger gears, there isn't really a need for additional power steering. That thing really turns smooth and easy. Of course you can not one finger it but I get by. I did have to drill new holes in the frame to mount it as the foot print was different. I also had to make a longer tab to hold the clutch return spring out a little farther from the frame to get around it. So it would be worth grabbing the steering box if you could. Someone could use it.