340 engine worth?

Locked up motor 50 to 100. If you take it apart and can verify that internal parts are salvagable aka a rod is not smashed through the inside of the block or there is not so much rust on a .060 over bore that the block is junk . 300 or more for known good core that is standard bore to .030. At 50 to 100 dollars it is a gamble. You may be getting a good rebuildable core or a boat anchor. If it comes with the intake figure 150 as you could sell the intake for that if the rest of the motor is junk.