Zooke is the Titan genius on this board, but I think he's off racing this weekend. Your 80xxx number sounds right for a 75 Titan. The 12xxx is an early engine... I'd say late 1969, early 1970. This engine will require tranny fluid capacity mod if you intend to use it. Early engines tend to eat 5th gear if used for a lot of highway cruising unless you do the mod. Check out Muzza's site for details. Will post on followup.