Looking at a pumpkin

I'm looking at this add on craigslist and here is what it reads:

"Dodge/Plymouth/Chrysler 8 3/4 (non-posi) complete pumpkin. This is the heavy-duty one with an 'X' stamped on it! 323 (freeway) gears. Pulled from a 1970 440 Dodge Challenger about 18 years ago and has been sitting in my garage."

I currently have a 7 1/4 which I am looking to replace. Will this bolt right up or do I need to fabricate or get different axles? I've never worked on a rear end so I'm not too sure about this stuff. I know that the gears are more for cruising which is fine for me. Is the 8 3/4 a good rear end or is it too much? I plan on making a built small block so just wondering if this is overkill or a good deal. Thanks again Fabo.