Yeah as above the cosworth,rs turbo all use the .42 compressor housing, but the compressor wheel trims are the following as standard. A 4x4 .60 compressor housing is slightly different to a 2wd one to accomadate the different wheel.
If a cossie exhaust housing then the actuator brcket has to be modded as the standard housing wastegate arm is in a different position to the cos housing. The cosworth exhaust housing uses a 3 bolt flange, I think the escort rs turbo uses a 5 ?

rs turbo t3
std compressor housing ar 42, compressor wheel trim 45 exhaust housing ar 36
stage 1 usually bigger compressor wheel trim 270 bearing.
stage 2 usually bigger compressor wheel trim 360 bearing.
stage 3 usually bigger exhaust housing .48, bigger compressor wheel trim and 360 bearing.

2wd cos t3
std compressor housing ar 42, compressor wheel trim 55, exhaust housing ar 48
stage 1 usually bigger compressor wheel trim 360 bearing.
stage 2 usually bigger compressor wheel t34 trim machined to t3 housing 360 bearing
stage 3 usually bigger exhaust housing .63, t34 compressor wheel and t34 housing and 360 bearing

4x4 cos t3
compressor housing ar 42, compressor wheel trim 60 exhaust housing ar 48
stage 1 360 bearing
stage 2 usually bigger compressor wheel t34 machined to t3 housing, 360 bearing
stage 3 usually bigger exhaust housing .63, t34 compressor wheel and t34 housing and 360 bearing