Stock heads are gonna limit you regardless of how much port work is done. You really need to Look at whats out there that is geared towards large CID. Then chose an intake the will work with them. Feel free to talk to people in the Cylinder Head industry before makeing a purchase. They may want to gaurd Proprietry info but in general I have always found them willing to open up regarding there products and what they have to offer. Richard@WCCH is really Good in this area. He has his own line of aftermarket heads that he does for different applications.

Stay away from other vendors that try and push there product on you with out first takeing the time to discuss your needs and your overall package.