Update. I pulled the power booster to get the rod out in order to get the screw in part free. A ton of penetrating oil and it was free. Oh yeah, the reaction disc was in place where it should be. I expoxied it in place just to be safe. I picked up a rebuilt '80 280zx 15/16" master from O'reillys. I did bench bleed it but that turned into a major mess. By the time I managed to get it in the car and the brake lines hooked up I lost all the fluid, I have no plugs for the fittings. Obviously I did not do this right. Fortunately the master I got has bleeders so I was able to bleed it back to itself on the car. I did try to adjust the rod according to the instructions I found here but even screwing the rod all the way in I still only get a small amount of upward movement of fluid, I am so confused. But I had to adjust the freeplay on the pedal quite a lot, probably the difference in the 280Z and 280ZX masters. I have good pressure on the pedal, so I took the car out for a ride. The brakes feel great, but its still an effort to hold the car at a light. I may have to lower the idle RPM a bit to make this thing "streetable".