Taken from this thread....
http://oddkiddcreations.co.uk/forum/...pic.php?t=6056
Would do you good to read as its almost the same setup as yours.
The 2wd Cosworth Turbo:-
Lager comp wheel and housing than the Std ERST unit.
The 4x4 Cosworth Turbo:-
Large comp wheel and housing than the 2wd and obvioulsy bigger than the ERST unit.
All Cosworths were fitted with a T3 shaft 2wd 3dr, 2wd Saf & 4x4 Saf Esc Cos (large turbo) apart from the small turbo Esc Cos which is a T28 and obviously the RS500 which had the T4 shaft.