Without getting all technical, here's a quick way to tell them apart:
The engine cowling has the heat shield completely contained within the cowling, with three slits cut out in the back of the fin.
This is the debut of the "cathedral" wing stabilizer design.
The engine cowling has considerable material removed to allow easier installation over the engine. The heat shield is now only a single deflector, and the fin has been narrowed (slits removed) and two additional "triangle" slits are added to the rear of the cowling instead.
The hull continues use of the "cathedral" wing stabilizer design.