Doing a few mods to a 2.0 blacktop head, mainly just having a go at cleaning up the ports.
On other heads I've worked on i.e. pinto and xflow I've always taken care to match the port shapes to both the exhaust and inlet manifolds.
On the blacktop there's a massive difference in the exhaust port shape and the standard gasket (and my new tubular exhaust manifold). The gasket is round and the port exit oval.
I have noticed that a lot of exhaust flange kits and performance manifolds are also round. So is the huge step in the (oval) exhaust port shape to the (round) exhaust manifold unavoidable and ok?

when i was doing my ST170 a while ago a local tuner advised me to leave the ports D-shaped so not to lose too much air velocity in the head. i haven't had it on the dyno yet so i can't tell if this was a good thing to do. but looking at the casting i think the exhaust port walls are very thin. and i don't think you'd be succesfull in taking away the D-shape without scrapping the head?

I think your tuners comments regarding the air velocity would be relevant to the inlet side only.
The exhaust may have to be left as a mismatch with the manifold as it would require a huge amount of material to be removed.
I thought of welding a tapered insert inside the manifold pipes to get rid of the step.