Welcome Paul and thank you for mentioning my thread! I've been trying to distance myself from the forum now that the bike runs and I've already posted lots of info, as I need to have find life beyond the forum! hahaha But as someone said, 'when I thought I was out, they pull me back in'! hahahaha
Yes, I see your bike is indeed in a similar state. You have the rear end complete, but miss the mufflers, I'd say it's a tie
I'd say clean the gears multiple times. Next time I'd probably use a hose on the gears after the oil pan is removed, then dry it with a hair dryer ans spray some oil on them so they are protected and safe to turn again. If they are already clean, visual examination and if all look good, and feel solid when trying to wiggle them in every possible way, I'd not worry about them.
The chains - it's in the manual and I can't take it off the top of my head exactly what are the numbers. Bottom line is to measure length of the chain between a number or links and see if it's within the limits. If anything needs to be changed, you'd need to split the cases, although people replaced the cam chain and water pump chains without it splitting the chains.
My wild guess is your gears and transmission are good.
Looking forward to seeing photos of the actual rebuild! How did you progress with revitalizing the cylinder block?
Lots of parts available from eBay. Some very expensive, some great deals. Sometimes what you are looking for is available only as a part of a bundle. I wouldn't hesitate buying the bunch and then you can post the left overs back on eBay or keep them as spares. I got so much spares I am thinking about putting together a whole engine, keeping it as spare, sell to recuperate the expense of this project (and that was a huge one), or wait for great deals which DO happen, and put another bike together and sell, to recuperate the expense of this project. I think I am repeating myself, LOL
You will have a great financial advantage if you live in the USA.
Good luck and looking forward to see the progress!
Stan