I gave up on RA after realizing that the shipping charges, estimated delivery times, and shipping locations were one big cluster and I wasn't really saving anything. Sure the parts prices are low, but to get it to you is roulette. Their website though is a great tool to get any idea of what's available. Get the part number and use the shopping function of google. Amazon, summit racing, and many others typically have the same parts slightly higher but in many cases free shipping.
I see this a lot, but if you use the tools RA gives you it's not too difficult to get everything you want from one warehouse for less than you can elsewhere.
For example, I am in the process of converting my 51 Plymouth to disc brakes. With the exception of the custom caliper brackets I bought everything from RA. The cost was less, delivered (shipping and taxes included) than any local source before taxes. I shopped NAPA, Autozone and O'reilly's, small town so limited options for local sources.
One thing to remember is that when you are looking at parts, if there is a little truck looking thing next to the part you are looking at it means that it ships from the same warehouse as a part already in your cart. See image for pinkish orange truck thing.
