Like others have said, Captain George's if just want to 10#'s of crab legs and aren't really concerned about anything else.
Wahoo's in Murrell's Inlet is really good. Not necessarily just seafood but they have good seafood dishes on the menu. Drunken Jack's has the hands down best hush puppies I've ever eaten.
My in-laws have a house in Murrell's Inlet so we get to visit pretty frequently. If you're looking for ribs, Greg's Cabana bar (on hwy 17) is supposed to be pretty good. I tried them as leftovers, didn't think they were anything special but all the retirees my in-laws hang out with down there seem to love them...
Thank you for the advice. We will be doing Captain George's for sure.