They never actually go off just flicker and dim until I go after light changes. Alternator or voltage regulator problem? Idle is about 800 rpm and Battery seem to start truck ok every time without issue.

 

Voltage regulator

 

2x... get a solid state (electronic) version. Google "Ford solid state voltage regulator".

 

Do the above and I would have the alternator bench tested with a load applied and ck the belt tension.

 

When I worked on British cars, we described the three headlight switch positions as "Dim, Flicker, and Off."

 

X2 on checking the alternator, it may not be toast.... Yet. Voltage regs are cheap. I would replace it. May want to do the cheap fix first and check all the connections. You would be surprised at how much stuff has loosened up over the last 30+ years.

Jeff

 

Yep Regulator. No more lights dimming. Thanks guys