REAR SUSPENSION TECH TIPS
It is very common for 64-66 T-birds to lean to the left (drivers side) probably due to the weight of the driver. Usually it is necessary to change both the leaf springs and front coil springs to correct this. Sometimes this does not correct it completely and the leaning side must be shimmed.
When changing leaf springs, always change all bushings and also the rear shocks.
Changing the springs will greatly improve the ride and handling of your car.