Heres how I measured what I needed.
I used the square on the crank pulley and I would swing it back and forth. I was able to determine what was center. Then I scribed that mark on both sides of the square on the PS pump, then marked the center of those two lines. (that represents the v belt center). Next I removed the pump and Installed the pulley I had, then used a small 6in, 100th in increments scale to measure from the flat area of the pulley to the scribe mark.
I was within .020 of his measurements on one of his pulleys!
It's on and looks great!
s/t