I first did this back in the early 1970’s to a Mustang I modified. I plan to do it again to my 1968 Mustang Fastback that I am converting to a Shelby Clone. This simple but effective modification will reduce body roll by between 5 and 10%. This helps tremendously when cornering and making sharp turns.
While you have the front end disassembled, it would be a great time to replace spring seats, etc.
The procedure was first developed and designed by Ford engineer Klas Arning who also developed the suspensions for the 427 Cobra and GT40.
The instructions for using this template are simple.
1. Remove shock absorber.
2. Compress the spring and remove it.
3. Unbolt the upper A arm and move it aside, carefully observing and recording where the shims come out of when you remove the nuts on the arms. You will need to reinstall them later.).
4. From under the fender, place the template over the existing holes. Tape the template up to the shock tower.
5. Drill a pilot hole for the new holes.
6. Drill out the new holes to the 17/32 size needed.
7. Install A arms (and put shims back).
8. Install springs.
9. Install shock absorbers
10 Get an alignment.
Here are a few hints to help you get this right. When doing the left side of the car, the template printing will be towards you. When doing the right side of the car, the template printing will be away from you. When you drill the holes, the new hole needs to always be towards the rear of the car by 1/8 inch.
Alignment information is +2 degrees positive caster, -1 degree camber and 1/8 inch toe in