[olddog]

First let me say I'm just an egg head that reads and thinks about engines. There are much more qualified people on this site than I. My comments are more to provoke thought rather than a recommendation.

I got the impression you are wanting a very street friendly, not too wild, engine. You did mention good torque over a wide rpm range, so I'm not too sure where you are wanting to limit the rpm. I didn't look up the cam specs (I'm lazy), but I assume it to be more to the mild side. From those assumptions, I'm guessing a 6000 rpm top end.

If you are going to limit the rpm to 6K, consider a 347 stroker. It would cost about the same as the 331. It would give a bit more torque.

An aftermarket block would allow you a 4.125" bore or more. That would set you back more money, but it would also step up the power and reliability. From what you said I doubt you are looking that direction, but thought I would put it out as food for thought.

If you step up the displacement, you may want to consider the AFR-185 heads, but KC would know what is best there.

You may be better off to error on the smaller side for a carb. I would consider a 600 CFM with what you described. a 650 cfm, if you go with more displacement.