If you have an auto I would put 3:73s, just so you can actually get some kind of gas milage. If you have a M6 definitly get 4:10s, but if you have an auto and dont care about gas milage get 4:10s anyway, you would notice a huge differance. Best places to order are Summit, Thunderracing, and TByrne Motorsports, just to name a few.