Gone Big Bore

I ordered some wiseco 700cc pistons today. It feels pretty good. I'm debating whether or not to use the 650 heads with 750 intakes or go with some GPZish Spectre750 heads that are ported. They supposedly have small combustion chamber, any idea how small compared to the 650?

I talked with a few people when I bough tmy 700cc kit, I guess there isn't too much performance from the 750 head to the 650, the cams are much more influential. But a gpz head is better, and the flow number are significant.