All of the exterior lights work on my vehicle. Up front, There is no power at the headlights but my parking lights and turn signals both work. I’m not a hundred percent sure how the wiring is on these vehicles. I had a 78 Cadillac years ago and had the same problem and it ended up being the high beam low beam switch on the floor. Are these cougars the same? Does the electrical run from the switch then to the high-beam low-beam selector then out to the lights? Should I replace the dimmer switch? Where should I switch the high beam low beam switch on the floor first? Also for extra information, my interior lights have been acting up a little bit lately. Sometimes They Come on Sometimes they turn off. Even sometimes when I turn the dimmer switch counterclockwise the lights won’t come on. All help is appreciate!. Thank you very much!
Also, all the headlights are less than a year old and none of them function. I even hooked up the older ones and they don’t work either
Yes on the high low beam switch on the floor. You must have power there for the headlights to work. Your dimmer switch might need replacing or just dirty. I have not replaced a headlight switch on a 67 but have done many 68 & 70, 68 and 70’s have vacumme hoses at the switch 67 does not. So should be easy compaired to the 68-70
thank you for the response! I will check tomorrow morning and report back with my findings! thanks for the info 
First check to see if there is power to your dimmer switch. It directs the power to either the high beam circuit or the low beam circuit. The power wire should be red with yellow stripe (it comes from the headlight switch). A green with black and a red with black go out to the light units. The wonky interior lights points to the resistance coil on the headlight switch. They aren’t too hard to replace and are readily available.
Thanks for the help. I’m going to check this out tomorrow… i’ve been been driving around during the day lately. Now that CA has done the time change it already dark around 5;30 pm! i need to order the switch from WCCC asap 
Is the old one plugged in? Any auto part store would have one. It fits all Ford products for many years.
the old dimmer switch? yes it is still connected
update update!!
So I swapped out the old headlight switch for the new headlight switch (purchased from WCCC) and guess what…? Now I have Headlights! so thank you for all that helped with the advice!
I’m going to resurrect this thread as I have spent all afternoon chasing an issue after I installed a pair of relays to put large wire juice to the halogen lights.
After installing the relays (I have 12 volts to the common on each relay and the old headlight wires (low beam and high beam) activate the coils of the respective relays. The high beams work like a charm but there are no low beams I decided to go to this arrangement because the headlights have been going out and then back on while driving at night. Assuming that the switch may be bad, perhaps caused by the additional current draw from the halogen lamps, and the headlight switch is acting like a circuit breaker which opens ad then resets itself.
There is no voltage on the green/black wire (low beam). I traced back to the dimmer switch and jumped the power lead to the high beams and they came on. When I jumper the low beams, there is nothing. I notice that the routing of the wires from the dimmer switch goes back behind the instrument panel before becoming visible again coming out of the firewall. According to the schematic, the power to the low/high beam comes straight from the dimmer switch but upon inspection of the routing, there may be more than meets the eye.
Any hints? I cannot, for sure, say whether the low beams worked before I did this. The last time I used the lights I had both low and high beams.
Thanks in advance,
Chuck
Ummm…green/black are high beams, red/black are low beams.
Ooops, got the colors backards in my description.
OK, I have voltage to the dimmer switch and jumping power to Green/Blk puts on the high beams but jumping power to Red/Blk does nothing. I have followed the wires up from the dimmer switch but the disappear behind a vent. They must come back under the dash somewhere (in order for the high beam indicator to function) and there may be a connector here where I need to check for continuity before the wires go forward into the firewall connection. Is this assumption correct, so far, and where is this connector located exactly?
Thanks in advance,
Chuck
Wait, I may have an answer. I jumped the low beam relay and heard it click but no lights. Don’t tell me I’ve just got a simple bad crimp from relay to headlights? More tofollow…
Found it…<duh!> Need to make sure that both relays are wired alike. Now working (no more wiring after dark for me). Sheesh!