Driveshaft MeasurementAll of Keisler's Perfect Fit kits come with a driveshaft. Unfortunately, they are unable to predict the future, so they require you to measure your specific combination. Not every '66 Mustang is the same, and most don't have their original rearends. You may remember the story we did on the Currie-built Chassisworks 9-inch that went into our Mustang. It has a different yoke than the original, so that needs to be taken into account. Keisler has specific directions for taking this measurement so they know how to build the driveshaft. They asked that we measure from the machined aluminum face of the transmission, to the flat edge of the rear end yoke. They also give a set of dimensions so you can determine your U-joint type. We came up with 52 inches using a 1330 U-joint. Just remember, measure twice and order once!