The bushings are all the same.
The A body suspension is identical in design, but some what different in component sizes. 73-76 a bodies use the big wheel bearings, which is why these spindles are so popular for disc brake swaps. Prior to that they used smaller bearings. Also, the A body lower control arm is actually about 1/4" longer than B/E body arms. This is another way to change dimensions to gain more camber/caster.