I assume you have a Ford-Thompson style pump setup, which was the main pump used from 1965 to 1977.
If you are asking if the later Ford C-II pump, made from 1978 to about 2001, will work - yes, it will. It has the same bolt pattern on the front, so it can fit the earlier style mounting brackets, but you may have to space the housing a bit or trim the bracket to clear the fins on the front of the aluminum pump housing.
The pressure hoses from the earlier cars won't fit the pump, though. The C-II fitting is a swiveling style, so you will have to modify your old hose with a different fitting to make it work.
No real advantage that I can see, other than the pumps are not as old, so there are more of them out there. They are a smaller pump, so that may give you some advantage around some accessories.
They are basicaaly like the earlier pumps in design, just with a smaller plastic housing and a swivel pressure fitting.
Can you run the P/S pump with no load no fluid without risking its damage? Got new engine and have no use for it (manual steering) but want to keep it prepared for r&p hookup.
Others here have more expertise, but I'm pretty sure that will damage the pump and fast.
I have a screwy belt set up where the pump is the only thing driven by its belt, so I'd just bypass it. If yours is part of a triangle you'll need a different size. With measuring tape and the old belt you can get one in about five minutes from the local parts house.
yes the early pulleys can pressed onto the C-II pump so you can keep your v-belt setup. i also don't see any real advantage to using this pump in place of the earlier pumps in fact they are generally quite a bit noisier than the early pump.
if you are converting to rack and pinion then you might want to consider a GM saginaw style pump from a late 70's bronco or mustang II some big fords had them too.