For anyone wanting to just get a PMA and electronic ignition on an XS with standard 360 degree crank, I would recommend "Powerdynamo" PMA with integrated CDI ignition.
This system can be run with or without battery, as the ignition is powered directly from its own coil on the stator plate, like on a MX bike, chain saw, etc.
This means that the centrifugal advance system can be removed, together with the points assembly, and there will be no wire running to an electronic unit mounted where the points are located. This again means that slimmer camshaft caps can be used, these are offered by Mule, Heiden, and possibly Hoos Racing.
A buddy of mine has a "Powerdynamo" PMA/ CDI on his -73 RD350, it has worked great for at least 3 years now. CDI gives a fatter spark than any battery powered ignition, and his RD starts really easy now.
Another buddy mounted a "Powerdynamo" PMA/CDI on his 1977 Moto Morini 3 1/2 Strada (350cc 72 degree pushrod V-twin) last winter. I just chatted with him on FB, and he is most satisfied with it. Easy starting, good voltage (bright lights). He is so happy with it that he is thinking about getting one for a Kawasaki KH 100 he has (Late 70-s 2 stroke single).
And I forgot to mention that I have purchased a "Powerdynamo" CDI/ PMA for one of my aircooled RD350s, and I also have a PMA ready for my XS, in combination with an Ignitech programmable digital ignition. (Powerdynamo do not make a system for rephased XS engines, that is why I want to use Ignitech with 2 pickups, triggered by the "lump" on the Powerdynamo PMA rotor.
And, no, I am not connected to Powerdynamo, Ignitech or Heiden in any way, except being a customer.