The squarer the engine the better it revs. More horsepower. Some race engines are over square bore is much bigger than stroke resulting in a high horsepower reving engine. Less torque than a engine of same capacity with a longer stroke but much better revability.

1200gxman take the a12gx out rap it up in a big plastic sheet and let it sit there as a exhibit and you can always put it back in down the track. Fit an a14. No cutting or anything just to steel plates used as spacers. A14 with higher comp, twin su's, extractors, cam and some porting = a pretty quick car. Thats what I have now and it loves eating 6cyl commodores and falcons in the 0-100km/h.

Anyway if you alter the GX its no longer a GX is it. Just go the easy option for horsepower. More cubes.