tamo3,
South Bay Driveline: http://www.yelp.com/biz/south-bay-driveline-san-jose?osq=balance+driveshaft
I did the same conversion as you, and I believe my shorten and rebalance was about $125. Out of my stupidity, it turned out that I measured my driveshaft wrong and had to bring it back for more shortening. They did a half-off shorten and rebalance for me for only $50. Great guys.