If your not going to change heads, porting the stock lower ia about all you need to do - guys have gotton to 240-260RWHP with ported intakes and heads and an exhaust and some are detailed in the Community section of my site in the Photo Galleries folder.
If your going to use GT40 heads, a ported stock intake is still a very good choice. If your going aftermarket heads eventually, then a Cobra or Performer are good choices now.