cam suggestion for hi-comp 340 and 3.23 gears

According to the parameters laid out, it would seem you could go as far as a cam that has up to 224º duration at .050". You may need a vacuum reserve for the brakes and you may be wanting a higher gear ratio (like 3.55:1) to take advantage of the cam. A safer bet would be 214º @ .050" as a limit.

FWIW: Comp Cams recommends you replace stock valve springs if you are going to use an Extreme Energy cam.

IMHO it is very easy to over-cam and over-carb a street engine. It shows as a lack of throttle response in the low to mid-range.