Don't bother porting heads, that's something that's fine way down the line once bolt ons are done, I've done it in the past to get small gains but were on smaller higher revving Honda engine!!
Times have moved on, casting techniques are much better and it would cost a fortune but the time there removed, flow tested on the bench then ported before re-fitting.
Exhaust/manifold mods would be far better.
Obviously all my opinion but kind of makes sense
Marcus