Mr. Arning and the Shelby Drop
First up, is the "Shelby Drop", or more accurately, the "Arning Drop", named for the Ford Suspension Engineer that came up with this mod even though Ford didn't incorporate it into the assembly line (probably because it reduces understeer a little). Shelby liked the idea, though, so he modified all the GT350's and GT500's of the same period with this improvement.
This is a common modification to all the early Mustangs that relocates the mounting position of the Upper Control Arm (UCA) bolts. Basically, you just use a template to mark and drill new holes in the shock tower that are about 1 inch lower than the originals and mount the UCA in there. Thus the term "Drop".
In the pic below, if you peek into the shock tower, you'll see two sets of holes that look like colons
The original factory holes are the upper set, and the new location is just an inch lower. Easy, right?
The entire purpose of this is to improve (1) the car's center of gravity by lowering the car right at the suspension mount, (2) improve the camber curve of the front wheels, which will in turn, (3) improve body roll control in turns. I'll just have to remember to use the Shelby GT350 alignment spec's when I set up the front end, not the original Mustang specs in the factory service manual.
All this for the price of a $10 steel template and the pain of getting this far into the front end of the car. I found $10 in the couch cushions, and I'm already all torn down to this point, so no problem. Plus, I already have one side done from the previous owner, so I'll only have to do the new passenger side shock tower and call it done! I'll knock this out in an hour, tops!