Tom,

They all start with the same airframe and are modified as follows:

320 = Lycoming 320  (slow version)
360 = Lycoming 360 (fast version)
360 MK II = 360 with the MK II larger all carbon horizontal tail.
(fast version with slightly more stable pitch authority)


Other major builder specific mods on these 3 aircraft could include the
forward hinged canopy, outback landing gear, Extra longitudinal
fibergalss bids occasionally seen on MK II to satisfy a flutter concern,
header tank (or not), outboard wet wings (making up for lost header
tank), Wet compass vs Garmin 430 etc. :)

Hope this helps.

Larry