Engine:
Head has better combustion chambers
Turbo is more efficient with different exhaust manifold to get rid of vibration problems.
Block stronger
Intercooler a lot bigger

Brakes:
Front: Reverts to sliding calliper from 2wd 4-pot
Rear: Vented discs instead of solid (carrier wider to accomodate)

Transmission:
MT75 gearbox with 7" rear diff (instead of 7½") and obviously a front diff, with different drive shafts at rear.

Suspension:
Rear beam different, front hubs and dampers different, different spring rates.