Well, the Wagoneer springs are definitely longer (47" vs 44.1/8') and wider (2.5" vs 2") than stock CJ springs.
Spring over you'd get some lift with the wagoneer springs but if I remember from my old XJs, they were already spring over and relatively flat. Is there any reason you're not using Wagoneer springs front AND back?
Vibration? Bump steer? Wandering? Read: Steering, suspension, and driveline basics. An article on how it works and where to look for problems.
83 CJ7, 4.1L 6cyl (4.0L bored .030" over), 35" tires, T-5 transmission, Dana 300 TC, Trussed AMC 20.