A few months ago I purchased from Camp914 a set of Pilot driving lights. These are being installed on a 75 chassis that has backdated front bumper. My question is regarding where to drill the mounting hole for the bracket ? I can't seem to find a " factory " dent or hole ? Anyone have a pic of these installed that might show the mounting bracket ?

sorry about the quality - shot with my iphone

The fog light mounting hole has a blind nut behind, centered in the lower square dimple. the two holes to the right are the bumper mounting holes.

The pictures are of a '74

Click to view attachment

Click to view attachment

Best method is to find an early car and make a tape template using the borders of the tape to locate landmarks common to both front fascia. Use a Sharpie to outline the hole and then locate the center of the hole with an X. Now, transfer the tape to your late chassis and center punch the hole.

The absolute best method to mount the bracket is to weld a flange nut into the hole you drill. McMark did this on my car and you would swear it is a factory installation. Rivnuts also work but I struggled with them until Mark welded those flange nuts in and now, it is perfect.

This is an interesting question, I saw the same question several months ago, as I am also backdating my '75 to the earlier better looking and lighter bumpers.
A smart person suggested the use of Self Locking Nut Plates that can be set in place with rivots. I am going to install my fog lights this evening, the self locking nut plates are easy and should work just fine. Welding a bolt to the body would also work.

Self Locking Nut Plates available from Pegasus Auto Racing Supplies, 2010 Catalog - page 102............... FWIW?

These are neat items that work for this application.

Vysoc

Oooooooooooor:

If you can draw a straight line, make an "X" in that little square area, drill hole. It's basically centered top/bottom and left/right.

If you can't weld a "T" nut in the hole you've drilled, I think you can use one of those heavy anchors. Ahh, I wish I could remember what they are really called???

Basically have two little plastic rods attatched to a metal plate that pivot. You slide everything into the hole, flatten it, put bolt in, pop plastic things off and done.

The pictures helped thank you. I went out to the car and found those raised square areas. Not trying to reinvent the wheel but would a large sheet metal screw with some blue Loctite do the same job ?

Probably not. You need the clamping force of a nut/bolt combo. The thingies I was talking about can be had at any local hardware store. Lemme see if I can find a picture of them.....

These, although you can only get them in SAE sizes, they can be purchased up to 5/8 or 3/4 bolt size I believe?

Something like a 1/4" would probably be just fine for driving lights.

I just finished doing the same back-dating a few weeks ago. I just drilled a hole, tapped it for a M8 bolt and stuck it on there. The metal is thin, so I didn't put too much torque on it, but it worked.

I'll be the first to admit that what I did is probably the worst option, but it has worked fine so far....and was pretty easy...

OK,

Mine is now complete, but the Nut Plate theory anchored by rivots does not work, too loose, and this does not mount the foglight flange flush to the mounting position. You need, as said above, the clamping power of a bolt/Washer/Nut combination.
After way too much thought, there is a way. Use the methods described above to locate the position for the bolt to hold the foglight flange. The "X" works well, mark the spot ...then put the bumper and grill back in position to confirm exact location.

Here is the trick part, drill your hole into the abyss below the headlight, where your Foglight will mount. Take out the spare tire as this will become your work space, there is a small slit about 1 to 2 inches wide where you can see into the opening in which you have just drilled. This would be best with two people, I did it by myself in about an hour after I dropped the washers 4 times. (once on the drivers side and three times on the passenger side). Have your helper mount the light and bolt through into the area that is not accessible, take a piece of coat hanger cut it to 8" and hang your washer on it. With a flashlight work the washer in place and hang it on the bolt. If you drop it take your time grab it again and retry, it is not impossible just another Porsche challenge. Once the washer is on the nut, grab two 3/8" ratchet extentions and put two universal (Knuckle) joints on the end and your shallow socket to fit the nut. Take tape and tape up the universals too fit the angle you need, all you need is to get the bolt and nut started. Once set add a socket, put a spacer nut in the bottom with a piece of tape to hold the nut about half way out of the socket, but in a position that will not let it drop out, taped from inside of socket. Once everything is in place you can hold the rachet with your left hand and thread the bolt with your right. Once you get the bolt and nut started... this was actually the easiest part you are in business. You can just reach the nut with a wrench to tighten down. This was a great challenge but everything ended up really secure and strong. Way too much thought though.
I'm glad it finally fits the way I wanted it to.

Vysoc .................Pictures to come

You DO understand that driving lights mounted at the height of fog lights will be useful for only 2 things, eye candy and blinding oncoming traffic, right? Fog lights, low. Driving lights, high. That's the rule.

The Cap'n