Josh's early gear cover has never been on this set of cases before. It's kinda "binding" and fits really tight. It's one of those things you mess with for hours, and finally get everything to turn smoothly and work correctly.
Bill's motor needs the front cylinder base stud holes modified to fit the cases (with no binding). The cylinders should fit nicely on the studs, with just a little wiggle room. If you have to force things, it's not a good idea since it may warp your bore or have a base gasket leak. Take your time, do it right is always your best chance at success.
I rode my '61 CH last night - then, after work I terrorized the town and went home as the sun was down with a beautiful full moon lighting my way !