Has anyone ever tried ftting belt-driven SOHC or DOHC heads
(watercooled or aircooled) to any aircooled VW engine?

All that would need to match is the bore-spacings; the rest would be
amatter of making it fit.

I know BMW experimanted with DOHC heads for its twinboxers, but it
wasn't workable because of resulting lack of cornering clearance.