Yeah finding wierd parts at parts stores can be a disaster. There's a couple different places to get parts
-The chepie parts stores, if it's not in the computer they don't have it, if you can't come up with a year/make/model for the parts monkey to put in the puter go else where. They are good for cheap junk parts that they don't need to be quality/ you don't plan on keeping for a while. They don't carry everything, good for cheapie tune up stuff, brake pads, u-joints, fluids, junk alternators/ starters.
-The "good parts stores" Napa, car quest, ect. real people behind the puter that will open up a book. This is where I go when I need an "odd ball" stock replacement part. They stock a ton more stuff and have books to find odd ball stuff.
-Off road shops, usually ma and pa places, it helps if your wheeling budies own the place, usually pretty close to competive prices. If you need shocks for something custom there's a 50/50 chance the part number is in their head and on the shelf or a day away. Good for things like gears, spicer joints, suspension stuff. If you get the right shop/ guy they can give you real world experiance with stuff and give you reasons why/ why not to buy something. The places I use i've wheeled with the owners, am on a first name basis, and even though they arn't in my town There's always ways to get big parts sent north to me or they'll ship and it's a day or 2.
-Online/ catalog places/ bigger off road shops. It's a crap shoot what you'll get, some times good some times bad. Unless you know exactly what you want/ need you might be wasting your time. Summitracing.com is pretty good and they have specs for some parts like shocks.
I use the different stores for different things. It helps when you are on a first name basis with the people that work at parts stores, I can even get service and help at the chepie parts store. I've worked in parts and it takes a ton of time to become good, be patient. People are going to be much more likely to help you if your paitent, crack a couple jokes and know what your talking about instead of yelling and not working with them.
If you need something odd ball go in to the parts store instead of calling, It's so much easier to walk in to the parts store and look through the book for a conversion joint then trying to do it on the phone. It really matters who helps you at the parts store, there are a couple people I dread working with and pretty much know i'm not going to get the odd ball part I need.
One thing lots of average Joes don't know about at parts stores is accounts. Parts prices are all about which account you use. If you walk into the parts store and they don't know you your going to get the "cash" price. If there's an account you can use you'll get a better price. Every shop in town has an account at the parts store, many clubs have accounts, they offer student discounts, aarp discounts, there's all kinds of ways to get better prices. It depends on the store on how flexable they are with accounts and how much of a discount you get/ what your buying. I've used the place I work at's account and at the chepie parts store there's probably 100 people that use our 4x4 club's account, we get a pretty good discount.