At 70 mph, the 3.31 is 1,990-2,015 rpm, the 3.55 will be 2,135-2,160 rpm and the 3.73 will be 2,240-2,275. Pulled from a spreadsheet I threw together at one point. Assumes 768 rev/mile on the tire, pulled from the specs for the OEM 17" Pirelli on the tirerack.com site.