For "Max power" & something that may be upgraded CID wise in future, buy the RP's & be done with it. The N20 will also eat up runner volume just like methanol does.

They come from ICH with 2.14" valves. They will be fine as far as hitting anything with the 4.035 bore. (won't be close)

Whether they will clear your custom Ross pistons, I have no idea, but if they were designed for the ICH head with the 2.10 valve I would think they put enough radial clearance in them to be ok with the 2.14. Call them with your custom order # & I'm sure they can tell you for sure.

You have alot of cam, & are spraying, the RP head should be fine. Just be aware there is very very little material at the top of the port for the intake to seal on.. if you try to reuse your current ICH intake & you'll have to make custom intake gaskets. We buy Raw ICH manifolds & surface them ourself to leave maximum width on manifold so it sits as high as possible on the RP head.