My guess is that it is worth from $1500 up depending on condition. Let's start with a running original that needs work but is complete and rust free, it will also have a title. $10,000 - not running $5,000 + no title $3500 + rust in normal places $2500 + missing tailgate $1500 - $2000 value. They are uncommon and hard to find in pristine condition so the market is whatever you are willing to pay, you will never know when another becomes available.
You must be interested enough at this price to consider it, so the next step is to investigate and evaluate it's condition. The tailgate is going to be one of the hardest pieces to find, expect to pay $1,000 and still have to do work on it. The rear sill/valence are always damaged and no reproductions are available. Original seats are hard to find and expensive when you do.
Depending on what you want to do with it also depends on what the price should be. Original parts are difficult to find, but some fiberglass parts may be available, modern driveline and frame may reduce the cost if you have a parts car available.
As uncommon as these trucks are to find in any condition there is still a very limited market for them. Not everyone that wants a truck will want one of these. Lot's of guys drool over them, but they don't put out the bucks for them. Good luck!
