yeah not too many counter folks aren't old enough to know a carb. And jets and PV for a Holley are the 1%'ers. I cant remember last I have even sold them. purchased quite a few though. At least someone there did have a clue though. I normally tell them when i'm buying it is aftermarket performance and not application specific. That's normally when I get called in. And I can take over and get them what they need but I've been in this on both ends for 38 years.
They do force you to rely on the computer system, but in the case of O'reilly they do paper catalog updates regularly (monthly). In the case of O'reilly ask for their parts pro/ commercial/ installer specialist for the weird stuff. Do you have a commercial acct with them if not just open a cash one it is easy to do and gets you at least a little discount.