Apparently the undersize shaft, whether one piece or two piece wobbles around enough to distroy the gears. Sounds like a disaster waiting to happen, which usually happens to me ruining an otherwise fun trip. The unit I was going to use measures .484" and slightly smaller on the lower shaft.
You'd think there would be stalled stovebolts piling up on the backroads of America. And as these inline six HEIs don't seam to grow on trees then the better solution would be to turn to Pertronix and keep the stock unit, NO?