I added a ground cable directly from my battery to the stud on the driver's side taillight mount. It is my understanding that this stud is responsible for supplying ground continuity for the tail lights, running lights and fuel pump. If a good ground connection isn't made here all kinds of weird things can trouble vehicle operation.
1. My ignition switch would get very hot due to a poor ground connection at the tail light stud
2. My tach would bounce erratically at times and odd surges would run through the system when the running lights were switched on
3. On hot starts the engine would cut out as soon as the break pedal was depressed or the car put in revers (break/reverse lights switch on)
Adding a nice thick ground wire to this post has eliminated all of these gremlins. Also check to make sure the ground between the transmission and engine is intact along with the grounds at each cam tower. Cleaning the ground pods on the inner fenders under the hood and adding dielectric grease should also be done as needed. I would recommend doing all of this along with the brown wire surgery and adding headlight relays to breath new life into 30+ year old wiring.
Fuel pump and taillight ground
Re: Fuel pump and taillight ground
all good points, but the headlight relay also saves the headlight switch from carrying all of those amps for the lights and failing prematurely