This explains it all for first gen Camaros. Same rear axle as ours except the camaro is 1 inch shorter in width as well. A perfect fit to the Nova. http://www.camaros.net/forums/showthread.php?t=188370

Here is a portion of it.
"68-79 Nova rear could be any of the following: 8.2, 8.5, 7.5 or 12 bolt.
68-71 were 8.2 or 12 bolt
72-74 were 8.5
75-79 were 7.5 or 8.5

Nova rearends are the widely proclaimed to be the"bolt-in" swap for 1st gens. However some Pontiac Ventura, Buick Apollo & Skylark and Oldsmobile Omegas and 77-79 Cadillac Seville also got the 8.5."

Mine is a 74. 8.5. Count on having to change your axles as well. In my experience they are usually worn at the bearing because the serve as the inner race.