The flywheel changed around 1982, nit sure when. I put a 1971 350 in my '82 K-10 a long time ago, purchased a starter for a '82 and ruined about 30 teeth before I could get my fingers off the key switch. Number of teeth is different or sumthin'. Had to replace the flywheel. "The flywheel changed around 1982" is what my older brother (Chevy salesman) told me at the time.