When you do pressure test the motor make sure you check for leaks at the
oil drains in the head. Im not real fimiliar with the FE motors but im not sure that block sealer would stop the leak at a head gasket for 6 months. You could possibly have some pitting from the
oil drain galley to through into the water jacket.
I know that would really blow and you dont want to hear that....lol..but just a thought.