To give you an answer you want:

You will need to consider these things!
1. Oil pressure! A normal honda oil pump in new condition produces about 85psi thats good for roughly 8500-9000rpms. If you want to rev higher you need more pressure to not go boom.

2.Bearings Bearings Bearings. Every bearing in there needs to be switched to a race version.

3. Yes build the head. period.

4. Also need to take into consideration the other ambiant flowing components. i.e. manifols etc. (maybe itbs for full advantage)

5. Remeber the other parts that have to spin with the motor. Transmission may go boom from the revs. Also i would recommend not having one of those super light flywheels (6lbs for instance) they have been know to shatter at high rpm abuse.

6. Someone correct me if otherwise but im going to assume that the H23 has no sleeves like the H22. High revs are going to be incredibly dangerous if that is the case. Aluminum doesnt like heat so you could easily end up with a warped cylinder and that would suck.

kk have fun and build. Hope ur wallet is ready.