Early vs Late 3v Crank Pulley Differences?

Tylinol said
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?
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Two things can differ:
The pulley/balancer bolt pattern changed in '70- one bolt was staggered pre-'70, pattern went symmetrical after that. Not a big deal, file 1 hole oblong.
Since the pre-'70 water pump (iron) was shorter than the '70 and later pump (aluminum)some of the depths/offsets could be different, depending on application- same goes for the pump pulley.