Go the 6l chev as it's alloy and the rover engine was originaly a buick/gm motor. It will be easier for parts and you should be able to get one on the cheap from a wreckers yard as "real hoons" quite often smash commodores/ hsv's into immovable objects at various angles that do not have any impact upon the engine.;)
This engine also give you the future option in the search for more power off supercharging(but cheaper and more power then the rover) with several aftermarket suppliers , walkinshaw racing included!

