Moldex billet, Crower, Callies, Mittler Brothers, Winberg, Sonny Bryant, Alan Johnson are who I'd call.
You've about doubled or tripled the price of a Molnar-machined Chinese forging. But when you start talking four figure hp numbers that's where you end up.
Out of that group I'd pick Winberg but it may be difficult to get into line at his shop, they sometimes have quite a waiting list. Realistically, I'd pick Crower for no good reason only that they have been around a long time and their billet stuff is hell for stout.

R.