I think it's been skimmed too far to be usable without racing fuel, unless the chamber has been relieved in the straight area opposite the spark plug. You can get away with around 50cc chamber volume with a D cam, but not a whole lot less.

Thick head gaskets are counterproductive -- the piston crowns need to come up close to the flat area of the head outside the chambers. Moving the head away from the pistons actually makes the octane situation worse.