too much to read, but if you mentioned getting the head tested disregard this. Otherwise, I just pulled my passenger side head due to a blown head gasket, and I brought the head to a Napa to have it checked. They do a pressure test to check for cracks and also check the the mating surface to be sure it is 100% straight. $50 and well worth it. If you didn't do that, I'm sure that's the problem unless it is a cracked block which is more unlikely.