I purchased a 74 Nova 4dr 350/350 as a donor car for my 69 Camaro. How do I know if the rear end is the good 10 inch 8.5 rear that I have heard some talk about?

http://www.novaresource.org/axle

If it is the original rear end then it will be the 8.5. The Nova got the 8.5 in '72 and all of them use it up to '76. That is when the 6 cylinder cars started getting the 7.5 10 bolt.

Freddie - Isn't there something about pinion nut size and left or right hand thread ring gear bolts?

Yes, but the 7.5 and 8.5 use the same ones. The 8.2 uses a 1 1/8 inch pinion nut and the ring gear bolts are 3/8 with 9/16 heads. The 8.5 and 7.5 use a 1 1/4 pinion nut and the ring gear bolts are 7/16 with 3/4 heads and left hand threads.