Big smallblock power..Turbo?
I suggest you start with educating yourself. The absolute best book out there for scratch building a turbo system has to be Maximum Boost by Corky Bell. It's not overly in depth on theory and is clearly written.
Prine is right,it's actually safe to run a turbo on a cast bottom end. buy Corky's book,read it and you'll understand why.
Amazon has em here.
http://www.amazon.ca/dp/0837601606/?tag=fabo03-20
Now,Im not trying to pump Amazon but you can get free shipping in the deal if the order qualifies.