I bought a reproduction tic toc tach, it cam with a seperate wire to run to the coil, way to short for a Hemi mind you, but it was included.
I thought this dark grey wire might be that as well...but there's no other end to it ??? If it was a tach wire then it should have been visable near the coil as well...


OK, back to the oil pressure question...The Hemi positive battery cable includes the oil sender wire...which section of the bulkhead would it plug into, if the gauge is operated by the circuit board?