No not really.---------XD was a marketing thing.---------Led folks to believe it was built for extra duty ( XD )----Some of these engines were built with a chrome plated bore and when things go wrong there it can be big $$ to repair.
About the only other difference you will find is the ignition switchbox on the newer motors. The switchbox will have different wire connections and maybe the mounting of them. Other wise they are the same except for some of the bores as Racer has stated. JMO
Oldman570