Novas have leaf springs & the rear ends won't fit, although internal parts from the pre-89 8.5's can generally be interchanged. A '68-'72 A-body rear end should be a bolt-in, but not all of those had 8.5's. I think Malibus finally got the 8.5 in '72, maybe earlier but I'm not sure. Look at the photo of the 8.5 & notice the heavy triangular protrusions at 5:00 & 7:00. Sometimes these protrusions look like somebody drilled a big old hole in it so there's just a partial projection left.
Here's a site with some ID info, & a couple of rear ends to avoid:
You may need a "conversion" U-joint & a slightly shorter driveshaft.