My parents owned a 1971 Plymouth Duster 340 when I was a kid. The car served as a daily driver for my mother at the time, an elementary school teacher, until 1979.
The story my Dad (who is 76 now) tells me is that he and my mother were out car shopping in 1971 and decided to stop by the local Plymouth dealer. Dad spotted a dark-rust looking orange Duster sitting in the back lot. He asked the salesman about the car. Supposedly, the salesman said a young 20ish guy had ordered it several months earlier after putting a deposit down. The car did not have any stickers indicating it had a 340 on it and allegedly, had some chassis modifications done. The salesman figured the guy planned on doing some street racing, hence the lack of 340 decals. Once the car came in, the guy informed the dealer he now had money problems and would not be able to purchase the car. The salesman said the car was now available. Dad asked for a test drive. One test drive and an hour later, my parents were the owners of a new Duster 340.
I remember the car as being very loud and would scare the [censored] out of me whenever Dad nailed it while passing cars on two-lane roads. To me, it seemed like the fastest car in the world...but then again, most cars are fast to kids who are under 8. I also remember thinking the car was ugly.
To this day, Mom and Dad talk about their 340. It usually ends in a heated discussion because my Mother wanted to keep the car. Dad ended up selling it in 1979 and bought a Toyota Corona (not to be confused with Corolla.) due to the '79 gas crisis. He also says that once Sunoco stopped selling their line of Sunoco 260 fuel, that the car just wouldn't run like it use to.
Dad still talks about how his little 340ci could give bigger engines a run for their money in a 1/8th of a mile.
My Mother's plan was to garage the Duster and give it to me when I started driving in the late 80's. Dad said the car was too fast for a new driver and that I would have killed myself and anybody riding with me. Instead of the Duster, I inherited the '79 Corona. It was a horribly reliable car that never landed me a date.
My vote is for the 340s