One thing for certain is, what the “correct” finish is inside ports and chambers is something that is not universally agreed upon from the industry experts.
Just go on YB or Speed Talk and you’ll find several proponents of a pretty rough burr finish.
Some prefer a finish that’s way rougher than how a TF240 comes.
I've had good results on iron heads with just shaping & leaving the carbide finish. No flow bench but a few buddies have picked up faster et's. I myself would just 80 grit the surface just above the bottom of the tooling marks.
