Long a staple of Mustang performance handling, the aftermarket is finally waking up to the Fox Cougar/Thunderbird with caster/camber plates. In conjunction with lowering springs, the plates will give a much wider range of settings for getting your car back into alignment specs, plus allows for better tire wear. Plus, you can have one setting for street driving, another for the road course, and another for the drag strip. They are available for the Cougar/T-Bird chassis through just one company, Maximum Motorsports, and they retail for about $200 US a pair, which is comparable to Mustang units.
One piece of advice: you must find a shop that can align the car using these plates. You will not want just anyone to do this for you. A complete set of specifications will come with the plates so that you can have the alignment shop easily get all your adjustment specs marked for you.
In case you're wondering, the plates won't really help much with a stock, unlowered suspension. They could help get a half-degree of camber or so, but that's about it. If you want them just for looks or to say you have them, you're not really spending money on something useful—you can get a lot more done to the car in other areas for the same amount of money.
Also, we've heard of several people that have modified Mustang caster/camber plates for their cars. While technically possible, they really don't do justice to our unique suspension setup. Considering that the Cougar/T-Bird plates are the same price, it would be rather illogical to use them instead.