It seems like a tapered reamer with the same taper would be the way to go. Just make a threaded coupler and then cut the taper in it, to fit on crankshaft. My question....is there such a tapered reamer on the market? Are you sure that the flywheel you have now cut down so the center portion is still there with taper, will not work good. All you need is 1/2 of threads and some loctite. Thanks Capt,n