This shows a comparison of the stock distributor (right) and the Up And Over Innovations modified GM electronic distributor. If you look closely, you'll notice that the new distributor has no vacuum advance. The computer (ECU) now handles all the ignition advance and retard functions. This distributor is slightly taller than the stock unit and might interfere with some dual battery trays. If it does, modify the tray. It's worth the effort to get EFI.