I had a 70 Duster my friend built. He had an MSD box but kept the stock ECU and wiring. If the MSD failed it took little to hook the stock box up and get home. I never had to use it. Wish my Hardtop Dart was wired like this as I did get stuck from an MSD box. Now running stock. I may go HEI and carry a spare. just my 2 cents. Nothing wrong with a well-tuned carb.