Hmmmm. At some point maybe sooner rather than later I will have to rebuild my Xflow 1700 Superspeed. I am going to spend this winter catching up on maintenance and replacing simple things like ignition, carb caskets, installing a catch can for the oil breather, etc.. Then drive for a season, mostly autocrossing, and then decide whether it is time for a rebuild and whether it will be just the head or the whole engine. Sounds like sourcing parts is the biggest issue. I don't like the idea of having to order several sizes of oversize bearings and using one.
One of the reasons whuy I like the Ford Kent is because it is used for Formula Ford, but there are so many Caterham-specific parts in my engine (the entire head, cam shaft, pistons, ...) that I suspect I'll end up with the same issues. Not something to look forward to.
Good luck, and please keep up with documenting the story!