Best advice I can give is for you to read a book called "Forced Induction Performance Tuning" by A. Graham Bell. Pick it up from Drysdales or somewhere like that. He gives excellent recomendations on all aspects of building a turbo car. There's too many sections on cam's for me to tell u them here, but I wouldn't have started my 4agte build up without consulting this book.
By the way, I am not A. Graham Bell or part of his family or publishers