Nobody's cutting anyone any slack today. Survival of the fittest definately describes BansheeHQ lately. But I think that's what this site needs.
You builder should be able to tell you exactly what size dome you need and Vito's should be able to supply them. I know nothing of the Vito's block or head, but I will assume they take a special dome.
You should contact Vito's, see if they can get you some blanks, talk to the builder and see what he would like the dome to be and get someone that can machine the dome to exactly what you want. There is too much power to be made and lost in the dome itself to go with a standard cut. That's not to say that a standard cut isn't right 98% of the time, but you have obviously steped up to a monoblock, pay the little bit of extra and get a custom dome built for your exact motor.