Knowledge about interchangeability has both saved me and made me a ton of money in the past. Back when eBay was still worth doing, I sold a lot of stuff at huge profit simply because I knew it would fit even if it wasn't correct, which I would always say in the description. I got around $300 for the painted Sport mirrors I took off my LeBaron though I could replace them for $20 three or four times over via my favorite boneyard. Pull the power trunk latch from an '88 Fifth Ave or any K-based car and watch the fun ensue when you list it for a '66-'67 B-body... no, it's not correct, but people love adding simple options like that just for the convenience. It's a bolt-in part and requires one wire run from 12V+ through a pushbutton switch. Buy it for $5, sell it for $80. It happened all the time, and the big profit is in the small stuff like that. That mirror-remote nut you just bid $40 to get for your '71 Charger? I pulled it out of a '79 Cordoba and the yard owner wouldn't even charge me for it. That "rare" correct vacuum reservoir in perfect condition you just gave me $180 to get your Air Grabber setup complete? Yeah, I paid $5 after pulling it from an '80 St. Regis. I also yanked the oil-pressure gauge that fits in a Mirada/J-doba dash and made $50 on that. Change the sender and use the original wiring. You're golden.
Everyone's car is special to them; I'm no different. However, that feeling often extends to parts, like thinking the upper ball joint in your '68 GTX is somehow worth more than the one from a Diplomat (they're the same part). No doubt there are oddball items, like '67 A-body steering arms, but in a lot of cases stuff just interchanges willy-nilly, or with extremely-slight modification if you're more worried about enjoying the car than a 100-point show winner.
I don't know why stuff like that sticks in my head... it just does.
