I second the idea that there is no way to machine the heads. The geometry
requires that the original surface be maintained.

The reason for this is that the head is "supported" by the cylinders not
the gasket as in conventional engines.

Removing any metal from the sealing surface of the head would make the
gasket seal much less reliable if not destroy it completely.

As noted, filling the pits with JB Weld is a good solution. There are some
good directions for doing the job in the archives.

Herb