The CT26 from the Gen II 3SGTE in both the MR2 and GT4 has the same exhaust manifold flange as the CT20B. The dump pipe flange on the CT20B has one extra stud but you can still interchange dump pipes. There can be some wastegate clearance issues though so check that the wastegate still opens fully once the dump pipe is fitted.
I have run a CT26 turbine housing on the Gen III 205 engine no probs.