I have been looking for the "right" bronco for over a couple of years now. I have never seen a vehicle that can vary so much in price. Location seems to be the biggest factor in price. Looking for 3 on the tree or 4 speed/granny, 351W or C, and twin stick transfer, body condition doesn't matter that much, niether do the brakes or power steering. I've found three like that in the last year but they're gone within a day and I've missed them all.
Here is a great website to find a bronco as well as anything else related to these:
http://classicbroncos.com/forums/forumdisplay.php?f=26
Here is one in Muskogee looks like a good start:
http://tulsa.craigslist.org/cto/2742191257.html