Pushbuttons use a different front upright ass'y than all later Panteras. Your steering arm is forged integral to the upright and the wheel spindle is removable. Later Panteras are exactly backward to this. To fix bump-steer on your car, I think the '73-up factory rack mount shims will work. If you're willing to do some work, the idea of lowering the rack slightly to level the steering rods can be measured so the exact shim thickness needed for a particular car is used, not a 'generic' shim thickness. The factory shims are the metric equivalent of 5/16" thick.
A second method is to use Ford-taper studs in the steering arms and shimmable Heim joints (with seals) on the steering rods, in place of tie-rod ends. This lowers the outer end of the steering rod to level it, leaving the rack undisturbed. The effect is the same, but lowering the rack also changes Ackermann- toe, which then alters low speed handing a bit. And manipulating the whole steering rack with extra mounting shims is really a two-man operation while using shims on Heim joints is almost relaxing by comparison. Don't forget to realign the front wheels at the end of the exercise.