I am running a power steering pump from a Mopar V-8 for my K-car power rack. This is the second time I blew the seal on the rack, could the pump be putting out too much pressure. If so, would putting a larger pulley on the pump help, reduce the pressure. I know they use a different fitting on GM pumps for the Mustang II racks.
Pumps create flow , resistance creates pressure. Most modern pumps have the relief valve set around 1000 to 1200 psi
The different fitting they use on a GM pump with a MII rack is actually a pressure relief. They drop it down to 7 or 800 psi from the 1200 or so that a GM pump normally puts out. So yeah it sounds like you have way too much pressure. Shimming a GM pump for less pressure is no big deal - you just add shim washers - they usually have 1 or 2 in there so you can copy them or just go to the boneyard and get extras there. I did that when I put PS on my '47 Ford - keeping the factory wheel was just too easy to steer - so I added an extra shim washer - I never put a gage on it, but you could take that approach too.
pressure way to high for a rack , the worm gears need high pressure to help push the servo , racks need about 1/2 the pressure as the pistons are on the rack itself instead of trying to push the worm along . they do sell a adjustable pressure relief valve to dump the excess pressure in the pump have to google it . last one I saw one it was in a ad for one of the car supply places . and pressure is varied depending on the rack ratio , a high performance rack will have a higher raio and needs higher pressure to assist
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