here is a link to another mopar site where another demon owner with the same SPD of 4/02/71 has almost the same dates of cast and the same assembly date as mine. also blue 340's didn't have the heat shield on the valve covers and the plug wire separators were painted over. http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=5798844&page=0&fpart=1&vc=1