There was some jackass on here a few posts ago that claimed you could get one rebuilt for about $400.... you may look him up as he claimed to be all knowing about the 700R4
But..... IMHO, your not gonna find one for under $900 unless its used. good luck in your search
1990 K5 4" lift, 33's, 14FF Detroit locker, D44 w/ posi, 4.10's Raptor Tranny and Velvet Rides....