The three lipped drill bits have three flutes instead the usual two. They have less of a tendency to drift off center and form a cleaner hole. Try "The McMaster/Carr Company". They have a nice on-line catalog. Shimming the worn surface is a thought of mine and is the last resort. I would use three, equal thickness feeler gauges (thickness as needed). Position all three of them to extend out the front and equally spaced around the crankshaft end. Coat the surfaces with locktite "stud and bearing mount" or similar before assembly. I would also use the locktinte on the pins Cut off whatever part of the feeler gauges that extend past the crankshaft end, before bolting up. This is not a factory recommended fix, but a last resort effort before complete tear-down. Success may depend on the extent of the previous damage. Make sure you get the counterbalance on correctly, do not get it 180 degrees off. You will see that the pin holes are very slightly off-set.
Good luck, and keep us up to date.
