Thanks, guys. This is just a replacement for an extremely sloppy, worn pitman arm. An outfit sent me the longer one (the only one they sell; a reproduction) after I asked them to measure it and they told me
5.25". They must have measured stud center to hole edge instead of hole center. I was trying to save the hassle of sending it back. It's going back because of the warnings from you guys. I just ordered a Moog K6151 pitman arm from Summit after Moog confirmed it was 5.25" long. The Summit catalog, though, shows this as fitting 5 vehicles, none of them a '69 Firebird V-8 with power steering. I've found nobody with a pitman arm listing for this car, and I've checked more than a few. I was even told that the reason for this is that '69 Firebirds used a pitman arm with no ball joint on it (thus it's a non-wearing part) and a center link with the ball on it instead. (The one I'm working on is not such an oddball.) I came to the conclusion the Moog K6151 matches my old one after reading the extensive webpage
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It's funny the range of advice I saw on this subject when I did some more looking. Ranging from warnings like you guys gave me, to "it'll work just fine; all the replacements are that long anyway," to "it'll give you faster steering - a good thing."
Thanks again.