Quick and dirty version: Spline count on the input shaft. It will be 23 or 18, and in your case, it will probably be 23. Hemis and SixPacks used 18. One of the few times that size really doesn't matter. Your biggest headaches will be finding a flywheel for the external balance 360 and getting a pilot bearing of some sort in the end of the crank. I'm running the stock /6 3 speed clutch with an OD833 in a 66 Valiant with no problems so far, but the slant is still stock, for now. :twisted:Cerwin said