found a 9c1 rear end complete for $250. Gavin called last night and said he thought the tires would rub on the stock xle, so 2" narrower will be perfect. here is where i got my info:
http://www.crankshaftcoalition.com/wiki/Wheelbase,_track_width,_and_differential_measurements rear track width (backing plate to backing plate): 91-96 caprice 60.7"73-87 suburban 62.7"