Connecting tachometer: Red from tach to igntion coil negative.White from tach to 123 distributor black.Brand new distributor with several different advance curves.Your original ignition coil can be used with this new 123 distributor, as long as it is in good shape. Keep in mind that this new item will give a stronger spark, which might cause worn cables and coils to fail. How to connect your 123 distributor