The Canfield heads are great

I've been happy so far, just would like a little more power

I think I can get you flow data on the 310 cc ports. Starting with the smaller ports is a good move. I reciently used the Edelbrock oval port heads on my 7.4 carb with mild pocket port work went up three prop sizes with no other modifications I push a prop usually used in a 502 in my boat . With cam and some headers I expect another 60 to 90 HP.

Yes, Jim & BJ do a great job. Jim can "see" air. # above is correct.