1965 Dart Questions

Ok Just brought the new project home over the weekend and have some questions. First This build will be a Pro- Touring style build. My first question is about the rear end. What is stock in this car? I understand the 8 3/4 is a much stronger unit, But is the original just to weak to put any power to it? Or is it that there are no aftermarket parts for the original rear? Posi?
Ok # 2. Just some quick measurements of the rear wheel well looks like you can stuff a 315 under the car with no problem. I understand the leaf springs are in the way. Thats no problem. I will just fab up some relocation springs. Anyway, I have seen a couple of other guys mini tubing theses cars and just wondering if there is something I'm missing on the rear wheel wells thats in the way.
I will start a new thread on the build pretty soon.
Thanks for any help you can give.
Tim