034 Motorsport sells them for the 32v engines, but not the 40 valves. Any help is appreciated.

factory head bolts.

I am not sure how the 4.2 is designed as far as having a robust head bolt but since the 2.7t started life as a diesel motor it is pretty stout.

Maybe also call ASP and talk to them since they have a project car that is a 4.2 with a SC.

Maybe they can even tune your ECU for you...