This is what the update is all about. The original holes are on the top. The new holes at the bottom are 1-inch lower than the originals. Whether you go with a negative-wedge kit or install the Blue Moon control arms, you'll be supplied with a template to ensure the holes are placed exactly where needed.
One of the more effective modifications Carroll Shelby did to '65 GT350s was relocate the upper control-arm mounting point in the car's shock towers. The result was more cornering power and a decrease in body roll.
As discussed on the Tony Branda Mustang and Shelby Parts Web site (www.cobranda.com), relocating the upper control arms can be done to any '65-'70 Mustang. The relocation, which lowers the upper arm 1 inch in the shock tower, was developed by Ford suspension engineer Klaus Arning. It was originally meant to complement the installation of an independent rear suspension (IRS) system that Ford experimented with for the Mustang in 1964. Shelby got word of the trick and incorporated it into all '65 and some '66 GT350s-through car number 252.
In more recent times, the idea has been taken a step further with the "negative wedge" theory that incorporates a relocation of the upper arm's ball joints. This can be accomplished two ways. One is to install a negative-wedge kit in a car's stock upper control arms. These kits are made by Pro Motorsports Engineering and are available at Marlo's Frame and Alignment. The other option is to install upper control arms that have the ball joint already relocated in the arm. The negative-wedge aspect of the conversion is incorporated into the arm and to correctly install them, the 1-inch lower holes are still drilled in the shock towers, so the geometry is accurate once the arms are installed.
With our '69 Mustang project car, we did the latter in a how-to story in our Nov. '05 issue. There, we installed Control Freak upper and lower control arms, which are made by Blue Moon Motorsports and available from National Parts Depot. At the time, we didn't relocate the upper arms in the shock towers, which in the final analysis, wasn't the best idea. We decided to correct the issue and show you how it's done at the same time.
With that in mind, we headed back to Marlo's Frame and tackled the project, which basically involves removing the upper arms and drilling the 1-inch lower holes in the towers. To make sure everything was correct, we installed another set of Blue Moon Motorsports Control Freak upper arms so the incorrectly stressed ball joints in the first set of arms wouldn't be reused.
Also note that this modification lowers the car's ride height 1 inch in front, which is ideal for better looks and handling. A 1-inch drop doesn't cause drastic ground-clearance issues or remove too much travel from the car's front suspension.