67 68 69 Camaro Chevelle Nova Impala 12 Bolt Gears 3.31 Chevy GM factory original 12 bolt rear end gear set Ring gear #3862689 13-43 Pinion gear #3862693 13-43 This gear set is the standard transmission set up for the Muncie 4-speed M-20. Will fit a 3 series carrier. The ring gear has some rust pitting marks at top see picture, $295.