What kind of horsepower are you looking for?
You can find a bunch of ebay or junkyard turbos to match. I found a decent Holset H2D for my LS1 on ebay for $100. It works great on my application.
For the 331 you could go Holset HX40.
Look here for more junkyard turbo information:
http://www.phpbbforfree.com/forums/v...junkyardturbos
http://www.phpbbforfree.com/forums/v...junkyardturbos