Have a question for you. I have a chance to trade for a 1974 Plymouth duster. The guy keeps telling me it has a 340 in it. He said it came from the origonal owner. He was told it had never been touched. The vin says its a 318. He took the casting number off the side of the block for me. 2780530-340-8 8-20-73. It is a 340 block. Is there a chance that chrysler slipped a leftover 340 in this car? Has this ever happened? Hebought the car from the origonal owner that said it had never been touched. The car is pretty rough and I just want it for some parts, but if it is a rare car maybe it should be restored.