Can I offer an alternative viewpoint?
Get a new alternator and don't screw around with re-threading the shaft. When you cut new threads you cut across the grain structure of the metal and if the finish isn't as good as original you create more stress raisers. Now you take this out on the racetrack and spin the crank at 7,000 RPM, so the fan is spinning at nearly 12,000 rpm, and you're supposed to be confident that the vibration isn't going to hurt anything? If the shaft breaks it's going to be a problem.
Stephen, LOL, the number of washers DOES mean the difference between wearing out the fixed half of the pulley on the fan, the alternator bearings and the #8 main. I hadn't heard that it had anything to do with carbon emissions, but to tell you the truth I have been staying out of the OT forum lately.
I also spent a few minutes today seriously pondering the merits of REAL cadmium plating vs. clear zinc if that gives you any idea where my head's at. . .