Joe,
There is a guy in Concord, east bay area, that can O-ring the head. I know he has done some stuff for Winspeed/Left Coast Diesel. The name of his shop is DDM (Don's Diesel Machine) and the owner is Don himself. He used to specialize in large diesel engine machine work on Detroit Diesel, Cummins, & Caterpillar engines, but he also does allot of custom machine work in engines for race bikes, muscle cars/hotrods, and diesel engines. Just give him a call at 925-372-8536. I hope this helps.
Regards, Mike.