That script on the hood is pre 1971.
If yours is a very early build '71 car, it might have come from the factory that way, but you never know with Dodge, they would use what was available at the time that the car was built........
Most likely, it is a hood off a '70 340 Swinger that was replaced some time in it's life for whatever reason.
Did the car come with the scoops from the factory?
The 340 emblems on the scoops are a '70 only item which points to me that the hood was originally from a '70, as well as the center script.
The blacked out bezels on the front of the scoops are correct for a '71 though.........
I also noticed that on the bottom of your dash, you have the reverse light.
That is a 4 speed only thing, so someone must have added it.
3 speed std. cars and automatics didn't get it.
As far as 3 speed floor shift 340 Demons go, they are pretty rare, but i used to have one.
I sold it to a friend of mine years back, it needed a full resto, but he still has it and it is slowly getting done.
It is pretty plain jane as far as options go, but it is a FC7 Plum Crazy Purple car, without the scoops and just a flat hood.
It also was an early in the model year build car, with the proper script on the hood for a '71 which is the same as the one on your trunk lid, just on the driver's side.
I hope this helps,
Tom.