News:
you will see the mounting hole on the lower left side of your bottom steel dash. left of the steering wheel
It goes by the ashtray.Your wire harness from the roadlamp switch will only go so far.The main wire harness will only let you connect it so far away from the relay.Connect the wires to relay from both harnesses and will give you a good location for the relay.It screws to the dash frame.THe 70 did have a relay.If you turn your high beams on the roadlamps will go off.
So, on a 71 cuda, if you want high beams and road lamps on at the same time, you should install the 1970 relay?
Note the 70 Plymouth service manual does not show the relay it must have been missed by the editors.
Here's a pic of the 70 harness