It's clearly marked on the schematic as coming from the tach, and going to the distributor. Although, I believe it has a black tracer on it. When I'm out at the car I'll check into it more.
It may be grey, what I'm saying is it DOES NOT go through the bulkhead connector. It should be on it's own individual grommet. Look it up. The 68 Plymouth manual is at MyMopar
