i will recomment 2zzge/2zzfe as its z generation.... as is the one of vitz..
for the a series i think you will need serious alteration as the intake/exhaust layout is on the opposite side in both the generations..
another factor will be the weight as 2zz-ge is a solid 30~40 kg lighter than the 20v, and the engine being in the critical position regarding the handling of the car, with 20v you will only have a drag car...
this is just my thinking and i stand here to be corrected....