I have seen them as low as 40 for tranny only, and 150-200 range for complete setup. Those are going prices from the 4x4 boards I frequent, covering WA & N/W OR. Personally I have a '76 10 spline adaptor & 205 setup for sale for $150 for the past 2 months.... no bites.
http://krazyk5.com/phpBB2/index.php
http://www.snort4x4.com/forum/index.php?s=
http://poorboy1.proboards31.com/index.cgi