BIG Turbo build planned - turbo guys!

At 25 psi, you ARE expecting to use a custom fuel mix, right? 8.5:1 CR will be marginal for those pressures, so I would go easy on milling anything, just get it straight, you can always take off more later if you plan ahead.

Why bother much with the porting, etc.? That is what the turbo is for. Just the larger valves are of value, IMO.

I have no idea if that engine will take that level and live for long.