Can anyone tell me how much i could sell a surface-rusted, maybe in stasis, 1966 425 Super Rocket engine? People keep demanding that i give it to them, but i think i should get some money for it.

 

If it's an M or N code engine it isn't worth much.
If it's an NS or NT code engine it's worth a couple hundred if it's in good shape.

If it's an NS code engine and still has the left exhaust manifold - The left manifold is worth more than the engine.