Power Steering Pulley

I am looking to put a twin groove power steering pulley on my Dodoge motorhome. I have a pulley I believe will work, but before I pull the older one off I would like to know if anyone knows the shaft diameter of the pump. This is on a 440, and unsure if that makes any differance or not. I could then measure the hole in the one I have and maybe save a little work if hole is too small. This is a press-on pulley. Thanks