If you are looking for a head that's done to limit down time my machinist does this on a fairly regular basis.. Although typically not w/ the cam etc already installed, however you could chat with him, see what he has on the shelf.
He's been machining Mercedes bits for some 25+ years and we have been dealing with him for just about as long. Nary a problem to report
Drop me a line if interested,
blueridgemb@gmail.com
Jonathan