Gear Vendors now has a bolt-in overdrive system for the FMX transmission, such as used in ’69-’70 Mustangs with 351W and 351C engines.

The .71 overdrive setup includes all electronics components. Expect a typical mileage improvement of around 25 percent. You can also split gears, effectively turning a three-speed automatic like an FMX in to a six-speed. The system fits using a factory trans mount and no mods to the tunnel or crossmember are needed. Gear Vendors Overdrive, www.gearvendors.com