Revolution Gear and Axle, Replacement series, Rear axle shaft for GM 12 Bolt Car 65-67 Chevelle, 67-69 Camaro, 68-72 Chevy II, fits both Left and Right side, 29.75 Inch 30 Spline (OE# 1239853). Revolution replacement series axles are made from 1541H Steel and utilize a state of the art computer controlled heat treated process. The use of better material and better heat treating process gives our replacement axles a 10 Percent increase over the OEM axles.