OCT 03-4100 - DRIVE FLANGE 1 1/8"-10 SLPINE 85 AND OLDER
Steel Chevy Drive Flange/Crank Coupler, 6 bolt pattern for 2 piece rear main crankshafts. Fits Bert and Brinn transmissions.

OCT 03-4120 - DRIVE FLANGE 1 1/8"-10 SLPINE 86 AND NEWER 1 PC REAR MAIN SEAL
Steel Chevy Drive Flange/Crank Coupler, 6 bolt pattern for 1 piece rear main crankshafts. Fits Bert and Brinn transmissions.