By their vintage design, '65-'70 Mustangs struggle with structural integrity. If you don't believe us, try this. Measure your door-to-fender gaps with the car on the ground. Jack one corner completely off the ground. Now measure the door-to-fender gaps. There will be some difference in the dimensions because unit-body Mustangs don't have a full frame like Galaxies and other composite-body cars, so they tend to flex. With unit-body vehicles like the Mustang, Falcon, Fairlane, Comet/Cyclone, and Cougar, the body and frame are an integral, welded-together, monocoque assembly.
When unit-body automobiles are stressed in hard cornering and rough-road conditions, their bodies flex and twist, which changes dimensions all over the place. This can adversely affect handling, not to mention safety. Global West Suspensions' solution to the early Mustang's structural shortcomings are subframe connectors--dual tubular bracing that bolster a Mustang's backbone to prevent the flex and twist so common to these cars.
For a closer look at how to install the Global West subframe connectors, we visited John's Mustangs & Classics in San Diego where Bill Nesbitt of Hard Core Hot Rods & Race Cars handled our installation. If you have access to a welder, subframe connectors are easy to install yourself and will make a big difference in your Mustang's structural integrity.