Have you considered swapping the entire head?
If the bolt hole pattern is the same you're part way there. You'd need
to pull your head to verify the mating dimensions. Likely the biggest
issue would be the worm wheel for side to side adjustment assuming the
series II has one.

Personally I'd suggest selling the head if that won't offend your
friend, and buy an inverter. Right now you mostly have to worry about
wearing out belts and bearings. If you think R8 tooling is scarce and
expensive, wait until you need parts for that head...


Jon