A strut tower brace will indeed help reduce
cowl shake. It will even make your car last longer sturctural (under normal conditions, the car will outlast you). Over time, a car will warp or twist and this is more pronouced if the car is driven under very hard conditions (road racing, drag racing, etc.) The negative advantage of this added ridigity is that the car will ride more harsh (you will feel the road more.) I have driven many Mustangs with such a brace and enjoy the many benefits, but do not plan to drive the T-Bird the same way I drive my Mustang.
That said, if you do plan to install the brace, I would look for one that bolts to existing bolts inside the engine compartment for the
coil springs. This way it will not require drilling extra holes or welding. Most racers prefer to weld them in, but that makes maintenance and removal difficult. This will also allow you to remove it without much of a trace if you felt the need.
As for everyone saying you should not modify your car, do what will with it. It is yours. You only live once and when you die God does not give you special consideration because you kept your car original. I believe that museums are in the business of preserving history.
Let us know where you find one and how it works.
Paul H., P.E.
02 T-Bird
85 Mustang GT Convertible