Help with fender apron to fender holes

[Zach]

Howdy. Been working on the mustang and want to finish up the engine bay. One of the last things I need is to drill out the fender adjustment holes. It is all new metal except for the shock towers so I assume those are the only factory holes left. Previous owner drilled out the driver side ones and they seem to align properly when I hang a fender from it. I am sort of lost on the passenger side and was wondering if there are any measurements or guides that can assist me. I assume one hole is for the bolts and the other a rubber grommet but not sure, driver side only has the oval drilled. Thanks, I’ll attach a picture for reference.

 

[Fabrice]

These are pitas to make for sure. The old piece should help you recreate them when it comes to space between them. The forward alignment can be extracted from the fender. A quick way to check side to side (from middle hole is the hood width minus fender L to side of the hole x2. Then cross measure distance from let cowl/pilar to first hole after radiator support. If the aprons were welded properly, there should not be much diff.

As about the holes. What the po did by drilling just one round hole is wrong. Not saying this for the sake of respecting originality. You need 2 per bolt. First because you need to secure the u-nut in the 2 holes. Otherwise you will hate the gym to install or align the fenders if you do not use u-bolts and secondly, the square holes allow bits of play sidewards to help align the fenders to the hood.
May you reproduce them, keep in mind the first pair after the rad support are inverted.
I would also fix the driver side..

To trace them the easy way, I did paper tape and draw them. The paper tape helps keep the small drill bit at each corner of the squares and after that, you can dremel cut between the holes. Small files help to fine tune after the drilling.

Good luck! It’s tedious but you won’t regret iat later stage to have done it right.

Edit: forgot to mention that if you need pictures or measures, you can dm me.