I'm refering to the standard 3rd Gen 276mm rotors and calipers.
Can they be made to fit the rear axle and will this pose any problems?

You'll need to work out a handbrake setup, thats for sure. Not sure how brake bias will be distributed with the fronts on the back and so on... Keeping in mind you'll also need to keep the standard brake distribution ratio, much fun :)

I'm refering to the standard 3rd Gen 276mm rotors and calipers.
Can they be made to fit the rear axle and will this pose any problems?

In short no, as luci said, handbrake assembly, hub is different etc, your better off getting the spacers off wookie, then track down AWD calipers and buy some DBA4000 284mm rotors for the AWD, Fit then enjoy.

out of curiosity, how do the magna's determine brake bias? Is it electronically controlled or is there a mechanical substitute for determining load on the rear brakes?

There's a mechanical proportioning valve built into all Magnas, with the exception of those with EBD, which can vary rear brake pressure on the fly.

aaah ok. Lots of older cars used a simple spring to determine load over the rear axle beam lol

Thanks guys. Will just go with slotted rotors for the rear with braided brake lines and QFM pads. Should be a good upgrade over stock.