I have a 340+.030 with the 3.58 crank and magnum heads and a mild Lunati cam. Comp ratio is 9.9 and a totally stock full exhaust.
It also has a Edelbrock intake and a 650 carb and I never had it on a dyno but I just don't see it making more than 300.
The 340 Barracuda's and Dart's in 68 ran 14:80's to 15:00 1/4 mile times.
