Are you talking about the pinion yoke, where the u-joint bolts up too, if so I doubt the monza and scottsdale have the same size pinion, if you are having trouble getting the u-joint to match up they make u-joints with diff. size caps.
Another option is to put a matching yoke on your drive shaft to fit the rear pinon yoke if you cant find a mismatched Ujoint. I doubt you'll have much luck trying to (swap) the pinion yokes.
On mine I had a 96' D shaft and a 69' rearend, they made a mismatched joint but I was going to cut the shaft anyway so I had them weld a 69' on the shaft instead, the joints are cheaper and easy to find.