I just did an upgrade from the stock '73 pump to a Saginaw and had to do both, remove & install the PS pulley. As said, the pulley is pressed on. While friends have said they've used different gear pullers to do the job, I've only had luck with an actual power steering pulley removal tool. To get it off use a decent puller & make sure it's installed properly (aligned straight & the "tangs" tightened down properly over the lip of the pulley). Most of the parts stores I've been to will rent/loan these out. It takes some muscle, this is a tight press fit.
For installation you can use a bolt + spacer setup, but the specific installation tool makes it so much easier. Saw one at Checker for $30'ish, but they might rent/loan this out too. Also helps to heat the pulley up a bit prior to installation.