THERE ORIGINALLY WAS CHANGE POINT FROM 72-74 1/2 ,IN THAT THE AIR PUMP BRACKET MOUNTED AT A DIFFERENT LEVEL ON THE CASTING OF THE WATER PUMP. IF YOU ARE STILL USING AN AIR PUMP ON YOUR 72-74 1/2 ENGINE, THEN THAT AIR PUMP BRACKET WON'T BOLT ON PROPERLY AND YOU'D NEED THE LATER BRACKET USED ON THE 74 1/2-80 ENGINES.
