Sagnaw Pulley - are the 2 types interchangable?

I have a 68 Dart with a 360 transplant. The Power steering pump needed replacement so i ordered one. The old one appears to be the press fit pulley and the new one has a threaded end. Other than that they are identical. Will the press pulley fit on the threaded new pump if I add a nut or would i need a different pulley? Thanks. Also wondering if I should do the "pump it down easy' adding the shim on the valve before I install.