PT the large idler spindle and alloy boss..throw them in the bin and get a two piece steel item. Your guesstimate at the shaft clearances are correct, and same for cam bushes to cam spindles. If your cam pinions are original well used ones throw them away and buy new ones...this will give you the hunting sound you described, due to the loading/ unloading effect of the valve train as the wheels ware over time. Set up each individual cam follower exactly over the cam lobes, and use shims as required to achieve this....NOT......just as per what the book says, sometimes you even need to grind some off the inner face of the follower pivot boss to align correctly with each lobe. Use new cams and followers if the old ones are worn, not many originals of either aren't, and make sure the ball ends of each pushrod spins and pivots freely in each follower socket, as they can hang up, not seated correctly down the hole causing tappet clearance issues....check same at upper tappet adjusters, as if these are tight, it can fracture the socket sides of the adjusters.......I think many of the finer dimensions you need, you are best contacting Clevtrev, there are probably less than 1% of anyone on this forum with the kind of details you are asking...Remember it is an air cooled motorcycle engine with some level of complexity over other engines of it's time.....You are not rebuilding a Merlin..I to have spent years in the aviation game, it is not an even playing field to compare a motorcycle engine to something that will plummet from the sky if something goes wrong. I understand what you are trying to achieve, I am just not sure it is easy to convey all that info on a forum. I look forward to your continued progress, cheers for now...........Greg.