I think in NSW you can only register an A14 in a 1200 ute, due to their capacity to car weight formulas, though it appears some people can get sr20 turbos regstered. You could either get an A14 for the same capacity as the A12 with A14 crank & A15 pistons, or put A15 rank & pistons in an A14 block for 1488cc . My opinion is just put in an A14 with your GX head. I'd talk to an engineer about what he'll allow before buying anything. He might be quite happy to register with an A15. Go for the one thats easiest, is my advice. In any case, dont forget the brakes. A simple swap to late 120Y struts with the matching master cylinder will give you disks if you have drums on it & any number of conversions exist for bigger brakes from there. I've used the 120Y PBR struts in a 1200 wagon with an A14 & they never let me down.