what heads and pistons are you using? 383's are a different ball game. they even fall out of the rules of norm for a big block. back in the day I raced them. very easy to screw one up compared to a 440. 340 pistons have valve reliefs plus a smaller valve and the valves open on the bore centers. it's good your not having an issue but from my experience with 383's and flat tops that cam is a potential problem. stock big block iron heads don't like higher lifts without work.
Are you asking about my 383 or his 340?