You want documented flow charts on a head is what I would look for. You can port the head, but if the port is not flowing like the others, or close to it, you are gonna be all erratic on the performance.
You have someone with a porting tool that hogs out the hole is once the air hits that open room that was once a closet, is the air slows down and your performance lags is the head (port) shut down the air speed is she was way too big and now a stocker would have flowed better.
Now, you have that head(s) so as to match-blend the intake and exhaust hangers. In other words, you are going to have to press a foot print from intake port to head port so no edge acts as a wall that the air bumps into. Because (the bolt on flowing parts, i.e., manifolds), are now you slow-down-hanger-on's. Your work begins is so much work now on the intakes and exhaust end hangers. Where now, you take the header or if you use a flange for the header, then grind that away to match the exhaust port. You got the drill...
Moving air fast is no easy job. It's how detailed do you want those (parts hanging off each end of the head) to match that air going in and heading out is make it flow as fast as possible is the key for the... Need for Speed.