A tranny swap is an option, but why not just change the rear gear? I had a 73 Mach 1 with an FMX auto and 2.55's. My dad kept saying that all I needed was some 3.90's or 4.11's, but I grew to like the 2.55's. Off the line; forget it- it would choke and puke. Stompin' it at 25 MPH would roast the tires on most surfaces. Top end was hell.

At the time, I traveled 20 miles each way to and from work every day, and lived out of town. It was usually 1:00 am when I got off work, and once I got past the one stoplight in the "town", I had another six miles to go before turning off of Rt 19 onto my sand road. I used to just fixate on the white stripes flying by me as the speedometer buried at 120. The speedo eventually broke, but I had it several times fast enough to where the front of the long hood would seem to sway back and forth slightly, feeling like the car was raising slightly at the extreme right and left sides. Dunno how fast it was, but it was well over the 120 mark, and quite possibly the closest sensation to flying I have experienced on the ground. Sixteen years later, it is still the fastest I have ever been. Looking back, I'm just glad I never met up with a wild pig or a deer.

Good luck,
Greg