GM indeed used two different starter snouts starting in the '70's. You can read about it on the Crankshaft Coalition - http://www.crankshaftcoalition.com/w...#Starter_noses but I think what you need is the starter with the staggered mounting holes (for a 168 tooth flywheel) as opposed to the one that's straight across (for a 153 tooth flywheel). I saw one note saying that they had luck asking for a 1972 truck starter, but can't say for sure. I'd go to NAPA and have them pull both of the GM starters that they list across the late '60's thru the '70's, with yours in hand for comparison.