For the record, from the factory, 1971 340 Dusters did not have hood scoops.
The Duster Twister did have hood scoops but the top engine in the Twister was the 318. The Twister was basically an appearance package available from the factory starting in the 1971 model year. Twisters, like the 1971 and 1972 Duster 340s, also came equipped from the factory with the sharkstooth grill.