Yep Cab is right. Look in junkyards and craigslist. If it's a dually rear end it don't matter, your going to cut the ends off and buy axels.. should find one cheep. There easy to cut down.
I been thinking about going to a 4.10 or 4.30 in my Avenger. Has 3.73s in it now. Turbos like gears too if u can hook it.