If picking parts, you also grab the GM coil and the cable which connects the 8-pin module to the coil, so no custom-wiring for that. The coil has a white wire for tach signal. Also clip the pickup wire and cable. The 8-pin module is inside the "small-cap" distributor. The pickup connector is not shielded but does have a locking clip. 8-pin modules will likely be available longer in the future since a 1985-95 GM part. The 4-pin is a 1970's part. In-between there were a few more GM HEI modules, like a rarer 7-pin. I don't know if the 8-pin has better tech, other than the input for spark advance, which you don't have to use. Read more on the megasquirt site.