If you have any more problems with the thermo housing, I’d be tempted to have the face tidied up, it looks like a skim would remove most of that corrosion.
That’s really sad to hear and I’m very sorry for your loss. He’s left a fantastic legacy for someone to take forward and finish and I hope your family can one day see it on the circuit and feel justifiably proud.
The oiler on the WD/C and CO is also an engine breather so angle it down. It should have a little disc in the block but I think these are often missed.
I’m certainly no towing expert but I think a good quality trailer helps with towing. I once borrowed a car trailer and it put me off towing until I had to do it again and hired a Brian James one. Totally different experience!
Engine oil is as good as any, you can see on some bikes, people tried to fit sealed chains but they are too wide and cut through the chain case. What ever you do, it will likely still leak.
I would try and source a good Cush drive clutch but they are hard to find now so may take a while. The non Cush unit you have now is from a much later machine, I’ve seen lots of them over the years.
This series is also handy.
https://www.ebay.co.uk/itm/115719615903?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=115719615903&targetid=1814673649102&device=m&mktype=pla&googleloc=1007079&poi=&campaignid=19089547614&mkgroupid=142438599285&rlsatarget=pla-1814673649102&abcId=9303859&merchantid=6995734&gbraid=0AAAAAD_Lr1cADOxPeV243zYz2lGaOTcP1&gclid=CjwKCAjwhdWkBhBZEiwA1ibLmPdDw0ORpn6G0MkZqHxyVaHEKgf3nVaQezgtf727OkFjNJopZli43RoCUIUQAvD_BwE
Have you got a copy of this booklet?
https://www.ebay.co.uk/itm/264392878563?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338343596&toolid=10001&customid=eb%3Ag%3Avms%3Aeb%3Ap%3A264392878563%3BCjwKCAjwhdWkBhBZEiwA1ibLmGj3D2r19XEiAFeOUS2fOmCtOW7sfXcvJeN1HvsW3Nl6fqZV4aYwvBoC1PIQAvD_BwE&gbraid=0AAAAADmMgighZP2AgDls66y9Geq23LcY-&gclid=CjwKCAjwhdWkBhBZEiwA1ibLmGj3D2r19XEiAFeOUS2fOmCtOW7sfXcvJeN1HvsW3Nl6fqZV4aYwvBoC1PIQAvD_BwE