okay, ive owned a ta22 with a 2t...i then put in a 3t.
While very simple (not a engine conversion, more an engine swap) i wouldnt bother as the difference was un-noticeable.
I do like the idea of a 2tg/3t hybrid though. With big cams/almost 2L capacity/big carbs/high compression/headwork 100rwkw can be achieved.
While this would not be cheap, it keeps the old schoolness of the car and would have more torque than a 4age.
Also, double check with local authorities the legalities of putting a 2tg or 3tg into your ta22. When i looked into this, i was told by the RTA that it would need to be engineered as, although it was a factory option, it was not an option in Australia...something to keep in mind.