I used to shift my 4 speed Duster with 340 at 7000 all the time. I had a Stewart Warner tach so I guess it was fairly accurate. That was in the 70s and 80s when I was younger and had the "it's going to go or blow" attitude. I was driving the Dart to the racetrack regularly and I wanted to be able to drive it back home. I didn't think 6200 was all that high for a 340.