My cousin pulled engine from his 68 300 with 80k miles and we found some strange and disapointing things. He bought this car last year but we have known this car from the 70s and has suposedly never had any engine work. It is a 68 engine but 1 has been apart felpro head gasket & rubber rear main seal. 2 has no serial # (replacement engine). 3 the strange part ,on both sides of block written in white are the letters CCCD. What does this stand for?