buy 4 rear lateral links for a 97+ grand prix. They are adjustable.
The 97+ link will bolt in and work no issues to replace the 1st gen rear arm
the 97+ link will not bolt in for the front of the 1st gen arm - but if you cut 1 inch out of the arm, and re-thread an extra inch (find a 55trucker post on this) they will fit no issues.
My recommendation is to match the length of the new arms identical to the 1st gen arm and you will have no issues getting it aligned. '
I have 97+ adjustable arms on the rear of my cutlass. the only issues I've had with alignment is when i installed them and they were the wrong length side to side. Make them the same as the 1st gen and you'll be golden.
The design for the Lumina/Monte Carlo items were altered from a rectangular box to what you see, the part #'s also changed, there's no cross reference back to the previous design.
the suspension member is still the same item as is the rear knuckles, the Monte's don't make use of the rear transverse leaf.