Measure the diameter of the input shaft and the spline count and that should get you started, the clutch dia will be determined by the flywheel size, any truck clutch and brake supplier should be able to help, not your local auto parts house unless they have been around for a while. While your there at the clutch house tell them what your doing, maybe a little sponsorship help, like their name on your sled. Tractor pullers buy clutches.
