Looking good Edward, I'm going to argue against the opinions of the previous posters and say that those inlets look like they've been "smoothed", as do your combustion chambers. It's a bit hard to tell as you've taken your pics with the head upside down so not much of the ports are visible, but I've got a couple of stock heads here and the casting marks in their ports are a lot more prominent than in your pics, so I wouldn't be surprised if someone's already done some work there.
Do you have an air compressor? If you do, don't fart around with Dremel tools, buy a cheap die grinder (20 bucks) and an Eastwood Company "Porting kit" (under 40 bucks)with the necessary mandrels and abrasive rolls, and you can clean those ports up even better, in only a few minutes each. As you've already seen, the aluminum in the CB750 head is very soft, so the abrasive rolls turning at 20,000 RPM remove a lot of material, very quickly.
As has been said previously, there's no need to remove the screw on the end of the shifter drum and there's no benefit in doing so anyway. Use a hammer and an impact drive to unscrew the other 4 screws though, and that won't be a problem. Use your hammer and an impact driver to re-tighten them as well. Don't go mental, just one whack on each of them after you've done them up hand tight will be sufficient. Merry Christmas!
