Any rebuild parts for a water pump would be a rare find. There are several
rebuild operations currently working. Other operations have decided that
there were no usable cores being returned.... in order to reduce costs, they
have forgone the added paperwork of processing useless cores.and started
selling new units.

Of you do run across those parts you need, be prepared to have a press and
some specialzed support tools on hand.

just my humble opinion.

Years ago I worked at a job where we had to rebuild some water pumps.
As Jim said, you need a stationary air/hydraulic press to disassemble
and assemble these pumps. Probably the tricky part is to find the
rebuild kits for a water pump. If you could find a source, you might be
able to rebuild it.
Seems like nobody is asking for the core anymore because it's cheaper
to get a complete new unit (the metal is prolly cast in China) than it
is to truck the core back to the factory.
I think you'd be better off buying an aluminum water pump from a
Mustang specialty shop than to have your core lying around waiting for
it to be reused, but whatever.
I recently ran into a Dodge starter where no core was needed. So I
guess they are manufacturing the whole new starter cheaper than sending
the core back to the factory to be rebuilt.

Fred,

Years ago you could buy these kits at most auto parts stores. It was just a
long bearing with a shaft sticking out both ends. You pulled the flange that
the pulley and blade mount to off, and push the complete assembly out the
back. Then you pressed off the impeller and put it all back together. You
had the measure how far the hub was on and put it back in the same place.
They were popular in the 60's. Did you try an authorized Ford rebuilder?
They sold parts years ago.

Al