Early vs Late 3v Crank Pulley Differences?

Hey everyone. I'm trying to find a suitable replacement for my '69 3-groove pulley (for my power steering/AC 1969 Barracuda). MAncini racing has one that looks like it would work CVF Small Block Chrysler Crankshaft Pulley - 3V . But, they say it's only for 70-later with the water pump outlet on the other side. For the life of me, I can't figure out why that would matter for the crank pulley. Does anyone have any insight? Could I actually use this on my '69?