PULLEY's

The '69 and older engines had the timing marks on the passenger side and used the cast iron water pump. When they redesigned the engines for 1970 to the aluminum pump, they moved the timing marks to the driver's side and changed all the pulleys and brackets. Just to confuse people some more, between '71 and '72 they changed from the staggered pulley mounting holes to the evenly spaced ones. That's why you need to slot the one hole if you swap between those two years.