Has anyone found a supplier for LED headlights (or brighter original style) for the 66/67 Fairlanes? I have the "original" style replacements circa 1990; when I drive with the lights on I can use my hi beams and no one flashes me since they are so dull.

Any help would be appreciated. Thanks,

Not personally aware of LED bulbs but your search would be for any 5001/5006 configured lamps. If your lights are dim, I'd be checking voltage at the plug. If you're not getting battery voltage -a very likely probabilility with all current running through the headlight switch, old wiring and corrosion on the terminals- then I'd suggest the conversion that uses the headlight switch to hit a relay for direct battery voltage to the lights.

I have read a couple of other places that Ford's of this era are prone to low voltage at the headlamps. Where would I measure the voltage drop at for a headlamp?

You could just pull the headlight terminal from one of the headlights and multimeter the voltage at the terminal. But since resistance increases with heat, you'll want to put a load on the system. So, pull a headlight and with the terminal connected to the light, multimeter the terminal from the rear with the headlights on. You'd like to read battery voltage at the terminal but you will always have some drop. A half a volt or less would be pretty good. It would be the most thorough inspection to do this will all the headlight terminals. If the drop is excessive, you could take the time to find out where the issue is but the smart money is on the switch itself. It should go without saying, but you have to monitor your battery voltage while testing to ensure valid results.

There is another way to measure drop; Negative multimeter lead to the positive battery terminal, the positive lead to the terminal of the headlight end and this will give you the actual drop, but this gets confusing for many since you're not reading actual supply voltage.

Thanks I will measure next weekend and report back