Well the tires may be the same diameter, but they are about 4 sizes wider which is probably where the rubbing is coming from. When turning your torsion bars up I would go in increments, i.e. 2 turns each, drive it for awhile, then if you like it cool, if not two more turns. This allows you to keep the truck geometry as close to stock as possible and still run those size tires. If you crank'em all the way the truck will be level, but you put some strain on the components and your ride will deteriorate. I believe Cognito offers a leveling kit for the Silverado, but it ain't cheap or easy to install.
JP
Jeff
"But officer, I ain't Speedin', I'm just flyin' low"
2001 Silverado 3500 Dually LS Ext Cab, 6.6L Diesel, Banks Stinger Kit, 4" Exhaust, VR Straps, Bilstein shocks, 255/85/16 BFG KM2s
2004 Suburban 2500 LT 6.0L 4x4, Bilstein Shocks, Federico front/rear sway bars
1996 Caprice 5.7L LT1, B4U Suspension, KYB shocks & Hotchkis sway bars, BMR RCA - alas I miss ya.
2013 Caprice PPV 6.0L