There is an 8.2 Chevelle rear on Kijiji for $400. I don't know much about it other than it's out of a 68-72 so it's 4.5" wider than the G body rear. An 8.2 rear end is good for up to 500 hp.
http://www.kijiji.ca/v-transmission-drive-train/kitchener-waterloo/10-bolt-rear-end/1180453875
http://www.kijiji.ca/v-transmission-drive-train/kitchener-waterloo/10-bolt-rear-end/1180453875