m code barracuda

I found what I was told is a m code barracuda . how do I know for sure ? car currently has a 340.the original 440 is supposed to be in the garage also . as is the original 4 speed . this thing is pretty rough any idea what it would be worth? the car is complete but rusty . I know nothing about cars at all . did they even come with 4 speeds from the factory ?