To anyone who has this issue, I can tell you how I solved replacing the outside (low beam) lower headlight adjustment screw assembly on my 69 Mach1 without having to take the whole extension and fender assembly apart.
So the adjustment screw holder broke off and I was left with the square hole and a stupid clip that is held into the fender extension by 2 screws which come in from behind which I could reach in and feel the screw head with my finger but this was NO WAY to get a screw driver in there to remove them to replace the clip assembly.
This is definitely a design flaw by FORD! (but not impossible to resolve)
So here's what I did-
1. Go into the wheel well from behind the fender extension and there should be a plastic splash guard held on by 4 body bolts. Take that out- now with the headlight and headlight cup out you should be able to see through the 5 inch round headlight hole to the front of the car, but you still can't get to the back of the 2 screws holding the adjustment assembly screws because they are blocked by a piece of the fender
2. I eyeballed up where the screw heads that were holding the clip should be on the other side of the fender.
I drilled 2 holes in the fender piece that was covered by the plastic splash guard large enough to get a shaft of a Phillips head screw driver with a screw head attached - (maybe A 3/8 OR 1/2 bit-)
Be careful not to drill too far or you'll puncture the extension (even id you do, aside from the aggravation, nobody will see it cause it will be under the replaced bulb when completed)
3. Take your Phillips head and back-out the old screws that at holding in the assembly. (They are probably going to drop and be unreachable inside the fender box but big deal. The plate of the broken clip will also drop too but does not matter either. Now you have the open spot where the new clip has to go but you need to get the clip there without dropping it inside the fender well too.
4. Ok here's the trick- get a piece of 24awg wire about 15 inches long, (I had a piece of telephone cross-connect) and loop it through the new mounting clip screw hole that would be towards the outside side of the fender. Put the adjustment screw into the square mounting clip too Now you have the clip assembly on the end of a wire that you can put in and snake down to replacement location and not have it fall into the fender void if you slip. Holding the wire loop, so you don't lose the clip inside, snake it down into position. Use a pair of needle nose pliers and pull the head of the adjustment screw through the square opening and into position. Now the adjustment screw is in position but you have to tighten down the assembly with the 2 mounting screws from behind.
5. Take a replacement screw and tape it to the end of your Phillips head screwdriver so it won't fall off easily. Using the adjustment screw as a handle to hold the clip in the proper place, line up the holes on the extension with the clip. Go inside the wheel well through the hole you drilled, and replace the screw on the mounting hole that does not have your wire through it. Tighten to the point where you're confident it won't fall out, but not too tight. Pull out the wire. The 1st screw should hold the clip in place well enough. Now with the wire out, Then tighten down the 1st screw. Then screw in the 2nd screw hole. You now have the clip replaced.
(I had and old clip from a donor car which did not have the correct length screws. I simply used a Dremel with cut-off wheel to make them flush- but if you bought a new assembly, probably comes with the correct screws.)
Now you can either plug up the holes you drilled, get a rubber grommet, or leave them as is- whatever. Put the wheel well splash guard back in and nobody is going to see the holes anyway. FORD should have done something like this in the first place! Re-assemble the headlight and enjoy driving at night!
This took me about an hour to do, but WAY better than taking everything apart.
Hope this helps-
