Wich intake manifold 4 a Holley600?

I would go with the edelbrock performer. The performer ports are matched in size for the stock 318 heads. Just bolt on and go. The performer rpm is matched for the larger 360 j-heads, they both have the same exact bolt patterns for mounting though. The rpm can be used but the larger ports on the intake will create a step where the intake and head ports join. Possibly causing turbulance and rough idle.....I am by no means an expert on this but just from my own experiences.

I have also heard that some people have had issues with the other brands matching up to the heads properly. I have used both the performer and performer RPM with no issues at all. Good Idle (on a mild build) and smooth acceleration.

pretty much exactly what "Rumblefish" said