They are only worth scrap. Send them to me!
All kidding aside the 302 motors are worth something to the right person. The civillian 302 motors are a little more desireable than the military engines, but both can be reworked to fit in the 1/2 ton through 2 ton trucks.
I can't tell you what they are worth, but the market trend seems to have inflated the prices of these motors in the last 1/2 dozen years. Location also plays a factor.
Good luck
John