I was recently lent a "fully recond" red K2F and must admit it was an expensive piece of junk, I was pleased to give it back and that it wasnt mine.
Sorting them out needs a combination of electrical and mechanical sensitivity that is hard to come by.
My race bike runs a new Hoe Hunt,
https://www.huntmagnetos.com/store/Magnetos%20-%20Ride%20With%20The%20Thunder!!/storeview_1278.html?id=78 but even that was a pig to fit, the flange plate was too thin and we had to mill the cases to provide clearance, but having done that am reasonably happy with. (have still had a coil failure)
The new flange plate we've slotted so timing can be altered without case removal.
I do also have a BT-H unit, not really suitable for methanol, but good for a road bike. Not convinced I'd do that again. It will go on my super rocket.
Personally I like manual ignition mags, not only original fitment for the RR and SR but nice to live with. My B33 has the old manual ign lucas mag and has a lovely low idle. But it hates rain!
another option is to fit coil and points if you have a decent generator but not a complete mag.
Yes they are all interchangeable, just some have an auto advance retard and the manual ones a fixed gear.