First engine would go good...in a Gemini, cant really picture it moving a Piazza too rapidly because of the weight. Anyhow, just a few comments.
The first engine isnt a genuine Piazza fitment - it possibly may be however it has been modified. There was a Piazza availible in Japan and the US that was fitted with a G200 SOHC, but the twin carbies are an aftermarket fitment. Standard cars ran i *think* an ECGI Fuel Injection setup...not sure, just know it was definately an EFI Setup.
Now, the G200 DOHC Itec setup...heres one i found in Melb ages ago, wrecker wanted 2500 for the whole car...which wouldnt have been worth more then 200.
In theory the DOHC shouldnt be much slower then the Aus spec Turbo, its only down 13kw but i think in reality its abit of a different story.
The Japs also "apparently" [im not sure on this one, so regard it as heresay] got an 134kw version of the 4ZC1 Turbo. Differences "apparently" come down to slightly higher static compression, a different variant of the IHI RBH5 and ECU Mapping [remember, the japs have had 100RON fuel for ages now]. Either way, atleast Holden got SOMETHING right and sent us the 4ZC1.
Nick-