[RichardJ]

>> ATP did come with a very rough casting, especially on the inside.<<

You are looking at something that is often debated.
To some extent,
"a rough intake port keeps the fuel/air atomized to burn a hell of a lot faster! smooth intake ports form droplets that as we all "should know" don't burn as fast or efficient".

A rough intake passage creates some turbulence, which can only help a single carb, long inline intake manifold. Inline engines tend to run lean on the end cylinders and anything that can help keep the fuel atomized is of great assistance.
Smooth, polished intake runner turns will have fuel droplets form when the air/fuel mixture tries to make the turn. Outside radiuses are sometimes dimpled to create turbulence.

Do not fully tighten the intake to the exhaust, until the pair are bolted to the head and don't over tighten.