340 identification

What year is the Duster? Most likely a '72 and '73 would have a "For 340 cast crank only" small counterweighted balancer.

Original engine paint could also provide a hint. But I'm not sure of the exact years and color changes. I believe 340's started out orange in the late '60's and went to blue somewhere in the early '70s'. Red sticks in my head for 318's. :scratch:

If the engine is suppose to be original, check the VIN. The 5th digit would be "H" for a 340 and "G" for a 318. If the car has anything smaller than an 8 3/4" rear or a 904 trans, it was likely a 318 car.

But comparing head casting #'s is a very good indicator!