I scored a ZR2 rear axle last week for $150 115,000 miles I found it on craigslist, a guy wrecked his truck and was parting it out. I have been watching car-part also for one and had a guy talked down to $250 for a rear axle. I don't intend on racing my truck or building a high HP engine.It has the same 5x4.75 bolt circle as the front and rear disc, unfortunately the guy remove it junkyard style(salvage yard they dissemble it) and cut the hose and E brake cables.
My brother runs narrowed 9" fords on a lot of his drag cars for the reasons Orrie said,I have seen one come apart but it took some serious HP to do it.
http://www.car-part.com/
Joe