If it does indeed have a blown head gasket you hafta automatically assume the head is warped, Ya need to pull it and if you don't have a machinist straight edge it needs to go to the machine shop to be checked along with a check for cracks and a valve job while it's there. But more than likely the heads cracked...
Easy way to check for a blown head gasket is find a shop with a 4 or 5 gas emission anylizer and check for hydrocarbons at the radiator neck, if hydrocarbons are present exhaust gasses are getting into the cooling system thru-head gasket or crack in head...
But assuming its original, the motors probally due for a complete rebuild anyway