1972 Plymouth Duster Alignment failure

If it is really going out of whack just driving off of the alignment ramp, then the idler arm is not likley the issue. The idler arm does not set alignment; it would only effect thing in turns. A pix of the idler arm against the pan would be worthwhile.

Ask the shop HOW they changed the upper ball joints.....did they press them out and in? Ask it just like that.....which is wrong, BTW....to see if they say 'NO (stupid) they screw in and out.....'.

Also, ask them at what point during re-assembly did they tighten up the lower control arm pins. The right answer is only after the ride height is reset and the weight is on the cars front wheels. If they tightened the LCA pins with the car up in the air and LCA's drooping then the LCA bushings may well now be damaged/destroyed.... that would likely mess up any alignment attempt. (And you are sure they changed the LCA bushings ??? That is a lot of work as the torsion bars need to be pulled back. Just want to be sure....)

And, the upper control arm bushings could be shot and will effect all alignment parameters. Shot strut rod bushings will effect caster.

As said above, they are doing something wrong in their procedures for the car to go out of alignment just moving off of the ramp. Or they tightened the LCA pins at the wrong time and damaged/destroyed the new bushings.