Have got a corvair with mid-engine 350, got a serious bucking problem at cruise.. holley 650, points style distributor, 4-speed manual.. very light car..
it idles fine, accelerates fine (even when you bunch it.), at cruise 2000-4000 rpm the car bucks pretty bad at times, the least bit of acceleration clears it out, but cruising at 45 mph drives you nuts, cuts into unpper rpms as you accelerate.
no kick-back on starter when you crank it.. no pinging on acceleration, no vacuum leaks (only thing off the vacuum is the vacuum advance)..