Power steering pump pulley. Press on or bolt on

So putting the 1970 duster back together and only part I didn't replace was power steering pump. And of coarse it leaks. Stopped by NAPA and picked one up for duster with V-8. Took old unit off motor and unit had a press on pulley. One from NAPA set up for bolt on pulley. Now what? Are pumps available with press on pully? Has the one on the car been swapped out with who the hell knows? Just wondering what anyone knows about this. Thanks in advance.