I previously tried to have a company rebuild my brake master cylinder. They sent it back saying they could not do it. I believe the problem is that it needs to be sleeved.
Today I sent the master cylinder off to another company that sleeves the master cylinder. This company offers a life time warranty. I am a little worried they will send it back because I took the unit part before sending it to them (they specifically asked not to do that) and I forgot how to put it back together. When I took the unit apart, I cracked one of the internal parts. I am assuming a rebuild kit would replace this component. This is the last rebuild attempt. I found another vendor that sells new units a little less than the previous vendors. I believe a rebuilt brake master cylinder is more reliable than the stock one. The company puts a more durable protective coating on the cylinder and the sleeve is more durable than the standard bore. When ever I do get a working brake master cylinder, I also plan on replacing the power booster, pressure adjuster and some vacuum lines. After I am done with the mechanical problems in the engine bay I will get the brakes rebuilt.