If that head flowed 291 @ .550 on my bench, it would be the same as the Competition CNC ported TFS 230cc SBC head with a 2.08 valve, flowed on a 4.00" bore, that I tested a couple of weeks ago.

Do I think that head would flow that on my bench? No.
But I also won't say it's out of the question.

I'm a firm believer that you can't really compare numbers from different benches.

Another thing is......
When they're your own heads, you can spend as much time on them as you like.
When you're having someone pay you to do it, if you take too long, you end up putting in extra time that you can't really charge for.
Porting a set of OE iron heads only commands so many dollars.
I can do a set of X heads in 20-22hrs. That isn't a "max effort" type of job, but I basic "full port and polish", including the chambers.
With a 2.055 11/32 stem valve they'll flow 275-280 @ .550 lift, without putting any holes in them other than perhaps the valve cover bolt hole.

It looks like you may have done more work around the guide at the roof, but then the X head has a better short turn....... Could be a wash.