What rear axle to purchase and narrow

Agree with a lot of the above, a Dana just looks right under a Mopar, a nine can be unbelievably strong, a 9 1/4 has a good lsd available, and custom axles can be had for almost anything, but.....
if you can do some or all of your own work, an 8.8, basically a copy of the beloved-by-the-chevy-crowd 12 bolt, can be narrowed, with gears, disc brakes, and a posi (sorry) for about a quarter of the price of the others, depending on what you find under an explorer, or mustang.
I have a Dana under one car, a nine under two others (both narrowed with a spool) and a 8 3/4 with gears and a locker. If I were looking (and I am, for a 57 chevy) I would absolutely get an 8.8 .
If you can weld, there are videos on you tube that show you how to narrow a 8.8 at home.