Another batch of updates from the last ~2.5 months (I should keep this thread more up-to-date)
So in the end the cylinder heads were also rebuilt. New valve guides were installed. Strangely the factory supplied ones had an ID of 6.5mm for the the 7mm, which were obviously too small for just reaming, so they had to be drilled up, then installed (heads heated, guides cooled in liquid nitrogen as per the manual) and finally reamed. There was pitting and corrosion on the surface. This was cleaned up as much as possible by resurfacing, but some still remained. In theory could have been welded up, but the places who looked at it were afraid about the material foaming up too close to the combustion chamber so kept as they were.
Unfortunately the machine shop did a pretty sloppy job with properly setting up the angles for the resurfacer so I found combustion chamber volume differences out of tolerance.
This was resolved by slightly reworking the chambers so we got into the ±0.5 cm3 range
Heads were assembled with new exhaust valves too
Installing the heads
After installation I remeasured the valve clearances (to account for the distortion). New shims are already with me, waiting to be installed in the coming weeks.