I have a sweet 1976 265 with about 90k miles. I drive it almost daily, but I have a reoccurring problem with a few of the idiot lights.
On the dash, sometimes very dimly, sometimes very brightly, and sometimes not at all, four of the warning lights will illuminate (charging, brake failure, parking brake & EGR)
About 1 year ago I had a similar issue and I changed the voltage regulator. That fixed it for a few months, then the lights started occasionally glowing again. Voltage from the alternator, as I recall, is a bit low, but it never fails to charge my battery. I did replace the battery and starter last year (as well as the external voltage regulator). It still has the marcels alternator. In the wiring diagram I did notice a voltage stabilizer around the dash lights???? Also, the yellow warning light for a burnt out bulb stayed on (though all the lights were fine). I eventually just pulled the bulb on that one.
Any suggestions appreciated!