How best to rotate this oil fill tube?

You might be able to try a heat gun on the manifold and twist it.

BTW who makes that tube??
I have been looking for one with the fitting for PVC so I can use my oem 327 valve covers

Most corvette or Nova suppliers. Some Chevelle venders. I thought about heating up the engine to.get the intake to expand at a faster then the steel tube to make not so tight. I wonder if there is some kink of tool like the oil filter removal tool that you could slip around, tighten, and rotate Titan Tools 21315 12" Strap Wrench.

I think heating the engine would also cause the tube to expand.. That strap wrench look like a good option.

Sometimes I’ve had luck tapping the tube back and forth with a rubber mallet and wiggling it out 🤷‍♂️

I would try wiggling it out and reinstall it.

Pull the intake and drive it out with a seal driver from the underside. Press it back in. I doubt you will be able to twist it.

Can it accept a 90° fitting so you can get that hose out of the sky?
That would clean it up nicely.

Like Humberd said . . . take a rubber mallet and smack it back and forth while pulling up on it. It will come out. Hit harder, you wont hurt it Then turn it and smack it back in. You can clean it off and put some green loctite on it if you want but I have never found it necessary. I pulled one out of an Oldsmobile manifold yesterday so I could shot blast the intake.

Don't add a 90-degree fitting on the filler tube. Like having a booger hanging on your nose. Correct the orientation of the filler tube.

Thanks to everyone for responding.

And is it done?