that stuff is out there. you just have to keep your eyes peeled. i saw an add for "dana 70 axles". no pics. took 2 weeks of calls and effort. the results where dana 60f, 14 bolt, 4.10s, and delivery.all for $600.
it's out there. but you have to look and be able to get there with cash in a hurry.
i'm on the hunt for a cheap 4500 myself. not in a hurry. this is an expensive hobby, and i dont have alot of extra cash just like alot of people on here. you have to be willing to put extra effort in. but it pays off in the end