•Lates ◦Stock is 22F ◦HD is 24 ◦Replacement stock is 26R ◦24F fits better in cars originally equipped with a 22F ◦Note: Be sure the battery has the notch for the hold down clamp. The Delco 'drop in' for a late Corvair is part #19002100. It is also called a 24R-6YR. Thanks to Erik Nielson for this tip. Hope this helps. Regards, Joel