[x-bird]

No engine sprockets lower than 11 are available that i can find---one of my first and longest searches. This one has an odd 6-spline 20mm shaft. In actuality, the rear jackshaft outer is the easiest swap--2 set screws.

The intermediate chain run interferes with the pull start case. I may "change that" by using the case as a mount for an adjustable or spring loaded roller tensioner and eliminate the need for different length chains with different sprockets. That would let me toss the pull start back on.

I'd be more than a bit leery of welding the clutch drum--pretty sure they're tempered and you'd have to get it on a lathe or end mill to get it concentric again. I put pieces self-stick sanding discs on my smoothest flat-profile rounded body dolly (the curve was really close to matching the drum radius) and used that to deglaze and knock down the highest portion of the grooves. If you're gasket shopping i'd get a couple for the clutch side of the case. I need to order a new one already. (going to get two)

As far as bearings, seals and other like items, see if you have "Browns Transmissions" near you. it's a chain, don't know if it's regional or national. I'm getting smaller sprockets at $6.00 ea and a 10-ft run of 50 chain cost $21.00--5 minutes from me--they stock Timken, National etc. They also had a metric seal for the crank--much better than the one i found at NAPA, but it still has a bit of a leak.--got to look at the outer portion of the bore hole.