Master Cylinder Bad?

[GunInstructordotcom]

My 1970 M35A2C had been sitting for about 3-4 years now. I fixed the hydraulic head problem that was causing the lack of use. Now I turn to the brake system and discover no brake fluid in the master cylinder. There was a black paste on the bottom of the reservoir. I cleaned out the paste with some giant q-tips I have for gun cleaning. I filled it back up with Dot 5. Looking from the bottom, the entire master cylinder is wet with brake fluid and there was a drip coming off the bottom. My guess is I need a new master cylinder. This one was on the truck when I purchased it in 2001 from a dealer in Idaho. He obtained it from a government surplus sale, so the master cylinder has some mileage and age on it. Is it safe for me to assume I need to replace it?

 

[NY Tom]

There may be a rebuild kit out there.

When I did the brake system I was able to find a replacement for a reasonable price.

 

[SCSG-G4]

The deuce brake master cylinder is a standard design, used in the GMC medium duty trucks from 1937 to 1959 (single cylinder), just like the M-37 brake master cylinder rebuild kit is the same as the 1936 Packard. BTW, the Packard rebuild kit is NAPA part number ONE as Ferro pointed out on another post.