Most "common" P/S leak on my Gm cars & trucks has been the bottom of the pump "can,they ALWAYS rust out at bottom!..nearly every chevy I've owned had a hole rust thru that resiviour....either that,or some moron punctured the side of it with a pry bar,trying to tighten the P/S belt...(which made finding a "good used one" at boneyards a real chore!).--many of my vehicles had that "can" brazed up,or patched with epoxy!..........................................I've had a few steering boxes leak some,but not enough to justify replacing them or trying to install seals...only once did I install a new pitman shaft seal and actually have it NOT leak again!...I opted to put a good used box on from a boneyard donor if mine had issues with leaks--I figured if it leaked,chances were good it was run low on fluid ,and internals might have suffered,so I just buy one that looks dry for 50-100 bucks used...