Why do the guys at the parts stores ask all those annoying questions? Because they want to sell you the right part and send you on your way. What do we hate more than anything? Returns. It costs us both time & money. It takes me longer to do a credit for a return than a sale, during which time I'm not selling anything.
Play along. Answer the questions. Help the guy/girl out, they really just want to sell you something. Is the few seconds it takes to explain going to cost lest time than a second trip, or a trip to another store? Think about it.
I used to sell parts and I can tell you that you don't make ANY points when you pull that "they're all the same" crap.
I REMEMBER a local guy WHO IS STILL IN BUSINESS came in one time wanted an clutch for "an early Ford."
Then got mad when I didn't "know" what "HE" meant by "early Ford."
DO YOU KNOW what an "early Ford" is?
Is it 28-34? 46-49? 50-54?
"All chivvy fuel pumps are the same," right? Yup, they will "all" bolt to the engine and pump gas, but not very many will fit some of the chassis, and if you are talking about some 'Vettes, they won't even fit in there.
Speaking of 'Vettes, did you know that you used to be able to buy a Delco dist. cap with TWO windows for dual points, AND a special "short" cap to fit under the radio shielding?
The front wheel seals on my 70 Plymouth RR were different because it was a six-pack car, or maybe because it had single piston brakes. NO body ever stocked 'em back then.
Back in the late 70's / 80's did you know that if you had a Toy pickup with BLACK WIPER BLADES that the pinion seal was different? Know why? IT HAD THE SPORT PACKAGE, and along with black chrome, 5 speed, bucket seats, it had a heavier duty rear axle
I sold parts for nearly 17 years and it's amazing that IF THEY ARE ALL THE SAME why we needed so many catatalogs, why so many parts always came back, and why we needed such a huge building to house all those "all the same" parts.