Find the Lightest one you can with no cracks - Have it Magnafluxed to be sure.
Doc Might have some more tips and tricks - He has ground down some pretty wild cranks over the years!
Drill the Main Oiling Holes with a long 5/16 Drill bit
Have your local machine shop turn and polish, balance it as needed.
I have a bit of a write up if you look down this page:
http://www.slantsix.org/forum/viewtopic ... &start=945
I spent a lot of time on that crank only to have too tight of a rod bearing ruin it.
I have to get another one of those made some time (when I have time )
Greg