So it probably didnt have enough oil at the time this happened or the bearing was defective. Usually the don't just split like that.
The kickstart mechanism doesnt seem to have suffered much
The cam chain tensioner is in good order
Heres a shot of the upper crankcase with the new part in place after having replaced the worn strip of metal that holds the bearing in place
The lower crankcase was filled with sludge and aluminum shavings... never something you want to find in your oil while you're doing an oil change.
Once I get the gasket set I ordered it's reassembly time. For now I'm concentrating my efforts on cosmetic things. The fender which was bent, a common problem with these 60s fenders the internet tells me, is now straight and the clutch and brake levers along with the handlebar perch have been repainted. Pictures of that to follow.