The 74 up went to the narrow belts & had different water pumps & therm. housings. About 68 up had the temp sender in the top of the cyl. head. Somewhere in the early 70,s up they had outlets in the head for air injection emission control. In 85 they put a emission system on that was the darnedest conglomeration of belts & pumps & hoses you have ever seen. Practically all that has been aborted by know.
