You do not need a "Triple" pulley unless you are wanting to add air conditioning
. The PS pulley fits over the top of your existing single groove crank pulley. However , its advised to use an era correct bracket and pump set to match the pulley. Several different offsets in pump and crank pulleys. Heres an example of the crank PS driver pulley.
https://www.ebay.com/itm/30312008093...MAAOSwsB9WBJmU