Yep, a decent catalog collection is damned good reference material. Quite often, if it is a store that still uses paper catalogs you can get the last years catalogs when they change over or have them get the ones you need for you. One other thing that I use a lot is http://www.oreillyauto.com You need a bit of imagination but for that combination plugging in something like a 1975 Chev C-10 with a 350 will probably bring up several clutch selections. http://www.oreillyauto.com/site/c/detail/SAC0/NFW1007.oap?pt=02271&ppt=C0338 Gives one flywheel selection. If you click on the top one and click "compatibility" you will see that it fits about 1200 combinations of Chevy vehicles. It is also a dual pattern flywheel for either 12 or 11 inch clutches but I have no experience with that brand. The thing is that by poking around a bit you can pretty well figure out what you are hunting for. And usually at most any parts house, unless you find parts man who is a racer, hot rodder or off roader they quite often don't have a lot of imagination as far as parts swapping goes. And the new breed who is either hired because they are computer functional or in a work retraining program don't have any concept that anyone would want to mix and match parts.