Crud. lost the end of my message. To continue:

Nothing short of a specially milled metal or wood block would be able to
sit against the mating surfaces of the head and cylinders to keep pressure
on them, and I seriously doubt such pressure would be enough to stop a
leak. Really the only way to solve a coolant leak at the head like that is
to pull the head, fix the pitting (or replace the head), and reinstall the
head with a new gasket.

John Bange
'90 Vanagon "Geldsauger"