Nice work. Lots of unique setups & remedial solutions there. Looks like your better judgment was already gazing ahead into the future LOL.
I think this demonstrates that 'restoration' can be quite a different animal that rebuilding or re-assembling.
I was going to ask about threads & fasteners in general - is everything old school Brit (Whitworth, BSF...)? What about even 'common' things like spark plugs, fluid caps, oil filter?
Interesting looking pistons, long aspect ratio by modern standards. I've noticed that on older aircraft engines of that era too. I was never clear why though. Seems like oil control & compression was still in concentrated in the top crown area around the rings, so why so much skirt length below? Maybe heat dissipation or related to materials at the time to maintain shape?
Does the owner have much in the way of documentation like shop/maintenance manuals?