Honestly? Not really. A better exhaust system will let your car breath easier over shorty headers. I have also already tried most headers. They DO NOT fit. You will run into problems on the passenger side with the center crossmember, and on the drivers side with the steering box and transmission shifter linkage. The collector is almost always in the wrong position placed too far up between the 2nd and 3rd exhaust ports. NO one has designed headers for a proper fit for this era Thunderbird. It's just not a popular year. Anything you get is going to have to be modified in some way for clearance. Count on that. Though I tried for a 429 in my 69 thunderbird. However the cars are identically the same frame and body wise.
The thing with headers is a lot of the people selling them are just selling the same thing others. They are simply suppliers and not the manufacturer if it themselves.