If you ask your late-model Mustang friends, they'll tell you that 3.55s are the minimum gear to upgrade to (remember, these cars have Overdrive), and many go to 3.73s and even 4.10s. But these cars also have 3,500 pounds to push down the street and only 300 to maybe 400 lb-ft of torque with which to do it. When completed, our Factory Five Roadster will weigh around 2,200-2,500 pounds and will have over 500 lb-ft of torque. With these numbers in mind, DTS recommended a 3.27 ratio to match our power and our Tremec TKO-600 transmission gears. DTS carries several brands of gears, but Ford Racing Performance Parts 3.27s (PN FM M-4209-F327, $248) got the nod for this build.