I sold one about 5 years ago for $400. It was a somewhat crusty rolling chassis that needed everything rebuilt.
Included were the vin plate, glove box door and a bill of sale from the yard I bought it from (probably enough to get a title in some states?).
In fact, I found that old post:
http://67-72chevytrucks.com/vboard/s...d.php?t=124333
If your chassis is complete with suspension and a current title to transfer, I would say you could get up to $1000?
Most people who have the desire to build a 2x4 blazer from the chassis up also have the skill to shorten a truck chassis, so it is a pretty small market.
Good luck, whichever side you are on.