Blown head gasket(s)
Warped head ( more common on aluminum heads)
Cracked head ( usually indicated by oil/water mixing in crankcase)
Cracked or split cylinder wall ( absolute worst case scenario, block replacement or sleeving required)
I would run through the list of things deuce gave you before moving on to these. If all else checks out, pull the heads and you'll usually have your answer.
sorry guys (my bad) communications, (that always gets me in trouble} I ment the symtoms of an engine that has already been overheated by someone else, and wants to sell it to me.
sorry again, and thanks oldnable