[jimjaz]

Best way is to post it to craigslist in your area and see what kind of responses you get. Try a $xxx or best offer. If it runs, and you can show that it runs, you have a lot more bargaining power. If it is truly seized up, then letting it go to the junkyard for scrap might be the best way to go unless you are willing to tear it down and rebuild it and spend a tidy sum of money.
Even if it is not running, and you post the truck for sale as a complete unit, people out there are interested in these old pickups. The vast majority would likely not be looking for a V6 per se, and would most likely be putting in their own power plant.
Good luck!