One of Those ads in Detroit have been on for a long time at that price so...
I agree with Bob, if one head is cracked the rest needs to be checked first before any deal is made. The salvage yard that I roamed through with Matt(Rattle Trap) last week had 3 Hemi's, 2 were under hoods of Chryslers and 1 was a Desoto that was exposed to the elements. My impression of the guy running the yard was that he didn't care about all the vintage stuff scattered around the woods and I can't imagine he would want much for any of it. If you pull the trigger and end up needing a head, pm Matt, I bet he'd be willing to help you out.