350 pistons?
I would not cut the tops on a piston for your engine. The reason being that the top is machined to a particular thickness to handle a N/A compression ratio. Cutting the top off severely weakens the piston and, while it lowers compression, it moves the top ring too close to the top, exposing it to too much heat. It also makes the top ring land too thin for a hi PSI TURBO application.
Compression ratio when under boost can come close to 20:1.
A thin topped piston will soon cave in at those pressures. Furthermore, a ring land tht's too close to the combustion chamber will distort and pinch the rings, causing massive blow by, even if it doesn't break.
Do some research and I think you will find most turbo, blower, nitrous pistons have the top ring at least .100 below the top of the piston.
The cast iron heads are about the 47-49 CC area.
Is the KB a hyper piston or forged?? If it's hyper and you are planning to "lean on" the motor, I'd go ahead and spend the bucks for a forged set. Hypers have to be run too tie in the bore and will get too tite w/ the heat from alot of boost.
My $.02 worth.