Need some help on pulley sizing

The Flowkooler will move water, it blew my Real Gasket out twice after installing. So went with the Flashpower o-ringed housing, that cured that. Do not know if the Robert Shaw 370 style thermostat let's more water through, but that is what I run. Pictures, Robert Shaw on the left, don't know what the one on the right is. It was in one of my cars when I bought it.

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