Depends a lot on what RPM your engine is going to idle at. According to Borgeson (and others who have installed) the loss of steering ease starts below 800 RPM (my engine doesn't like to idle at less than 790) and doesn't get to be real bad till you drop below 675-700. On mine, I spaced the P/S pump out to use the larger diameter groove on a three groove pulley, so I am assured of a good pump speed! Also, many/most of the later model pumps (with flat serpentine belt pulleys) keep up a better pressure at lower speeds and IIRC, they will bolt onto an early bracket and have the same shaft size as the v-belt pulley. Also it keeps that "G"eneral "M"ess of "C"rap stuff off my FORD. I'm not often "snobby" about brand names, as I own several brands, but I AM SORRY, Chebbie Parts belong on a Chebbie, Dodge parts on a Dodge, etc!
Gene