The Saginaw (oval neck) power steering pump is the one to get. In later years it was squared neck. You can also drill out the spool valve hole 1/64" larger than original to get more flow.
The Federal units do not keep up with sawing the steering back and forth quickly in an autocross.
If you can, later plastic Saginaw filler caps have a rubber baffle in them. I've even seen them at the parts store in the HELP section. You may have to mark a new fill level spot to match your original one. The quick turning in an autocross can get the P/S fluid to splash out of the cap. Sometimes even foam, so your good quality P/S fluid.
