It's quite common for folk to convert the XS650's old points & coil ignition to the new fangled electronic ignition, but here's a step that kinda goes back in time by converting the system to a magneto.
On flat-track Triumphs, the Americans often used to remove the original luacs mags, and fit (in a different location as the drive take-off pont was changed) USA-made Joe Hunt mags, which were kinda 'box-shaped' compared to the K2F Lucas round barell design.
Well, if your bank balance is strong enough (currently advertised at $979), you can fit a 'box-shaped' magneto to a XS650 lump courtesy of Morris Magneto.
http://shop.morrismagneto.com/products/yxs-for-yam-xs-650sCouple of pics from the Morris Magneto website