They changed quite a bit on the LST2. Engine and wheels were only the Imediately obvious changes.

The Rear axle carriers are now fixed, meaning no more need for a rear turnbuckle.
The Axles are now 8mm and use a 20mm Hex.
Wheel bearings are now larger to accomodate the larger Axles.
Axle carriers all around are now larger and stronger.
suspension arms are beefier and stronger than before.
Stronger Chassis Main Rails
Included secondary gear cover
Stock threaded shocks


I'm sure there are more...