If you don't plan on taking it off-road much and are not suffering from Wag-Sag then you really don't need a lift to run 31's. I'm running them without a lift and only had some rear fender rubbing if I flexed it off-road. I will be adding a lift to cure this but only because I do take it off road. If I didn't I wouldn't bother.
1989 Black Grand Wagoneer, BJ's 4" lift, ProComp ES3000's
31x10.5x15 BFG AT KO's,MSD 6A,TFI upgrade,360,727,229,2.72 gears.
2006 Dodge Magnum R/T
2000 Jeep Wrangler
1988 Cadillac Brougham
1966 Dodge Monaco 500 383
1965 Pontiac Tempest 326