Also, you can pick up those three AMs you mentioned all over the Carolina Coast. 630 can be heard all the way into the Myrtle Beach area well, before the 630 from Wilmington starts interfering.
900 would have one of the best signals, but it goes out around Georgetown due to WNMB at 900.
From where I live (near Charleston) I can probably pick up two dozen Florida stations every day, especially by the beach. I can pick up everything from WOKV (which has one of the best AM signals on the East Coast) to little stations like 1590 in Daytona Beach (with 1000 watts), including almost all of Jacksonville's AMs.
A couple that you should try are 1420 in St. Augustine, and 760 in Tequesta, FL (West Palm Beach). Those are huge signals that can be heard almost all the way up the coast into the Grand Strand. I hear 760 every day, even though I am 400 miles away from the station, with only 3000 watts.
I can also hear 610 from Miami most of the time weakly, and the ticking clock from CMCA, like most people along the East Coast S of Virginia Beach.