Scratch in front MC bore '79 GS 1000

[jknappsax]

I just got back in town from a 2-week vacation, and started on figuring out why I could not get the front MC to develop any pressure after bleeding my rebuilt front caliper. I finally got the MC circlip out (my circlip pliers wouldn't reach in deep enough; neither would any of the others at my local True Value hardware store) and as I'd suspected, the rubber was very worn, so I know I must rebuild, but there's a score in the barrel parallel to the axis (which you can feel with with a fingernail), and a couple corroded spots. I can't get in and hone the surface with a honing tool, or if I should even do so; I'm worried that the rebuild kit won't be able to work if I remove enough material to make the bore surface good again. The bore size seems to be 14 mm, if I'm reading the number cast into the outside of the MC. Any opinions on whether this could work?
I have a MC from a 1991 GSXR 1100 which seems to work very well, but I can't get the two f*****g phillips screws out. I soaked the area with penetrating oil (Kroil), tried first to use my impact tool (but just buggered the heads), then using a Grabit. No luck. It's useless if I can't refill the receptacle with new brake fluid,. If I can finally get out the screws without destroying the GSXR MC (which has a 5/8 bore) would this MC have decent enough lever feel to work with my single caliper in the front? Any input would be appreciated. TIA.

[Nessism]

Scratching and pitting in the bore is a deal breaker. I'd trash that thing. A 5/8" master will work but the hand pressure will be higher than using a 14mm master.

[jknappsax]

I did drill out the screw heads on the '91 GSXR mc, and got it to the point where I can work with it. Now I need the screws to hold the cap on. I'd really like to use screws with turnscrews to be able to add fluid by hand without having to take out the F$#@%^&&g phillips screws. Since they are flathead phillips, they've got to have the countersinks to match the cover. The weirdest thing about the GS mc is that the lever felt good up until I used it to pop the piston out of the front caliper, then after that, NG.