350 hp out of a fairly stock 340

I can guarantee you a 68 383 S barracuda with hooker fenderwells will walk all over a 340 car.
4SPD/ 3.55 gears.
I won't argue that. I think the main reason a 340 A body does so well against the 383 Road Runners is the weight difference. I had always heard that the driver's side factory exhaust manifold was so restrictive that it really hurt performance. I bet adding headers to one of those back in the day would really have given you a big seat of the pants feeling.