Ok I have a serious problem. While doing some maintance on my super charger I noticed the crank pulley was loose. Meaning I could turn it by hand after the blower belts and all were removed. So I tore it all apart and found that the key is broken in the keyway. Now the engine was acutally running fine prior to this, there must have been enough friction to hold it all together. (Car is just driven on the street- no racing)

1. Anyway I'm wondering if this repairable for an engine that's making 600+ Hp with a 6-71 Blower or should I just be replacing the crank?

2. The crank is internally balanced, if I buy a new internal balance crank doesn't the entire assembly need to be balanced with it?

3. What crank would you reccommend, forged, cast etc, and could I put in a 4.00 stroker crank instead?

4. How can I prevent this from happening? And what happened?

http://www.rlmdigital.com/photohost/Key1.jpg
http://www.rlmdigital.com/photohost/Key2.jpg
http://www.rlmdigital.com/photohost/Pulley.jpg
http://www.rlmdigital.com/photohost/Crank.jpg

Thanks for your help, I'm sort of new to street rodding and learning as I go. :-)

Car info:
'28 Ford Model A convertable
402 Chevrolet Big Block, GMC 6-71 blower, Muncie trans