Are you sure its an XB motor? XB's use a different mounting setup that is unique to only the XB frame. So unless you have a frame designed to fit an XB motor (like a Bottpower or Ludwigsen), its probably just a Sportster motor.
If its been converted to carb, you're probably better off just converting it to an older Sportster style ignition, unless the XB motor is from a 08-10, which it going to make things a hot mess.