Looking for one myself for the 1967 C10
I tryied what you said in your first post and it does work but not
that well. I get sticking a lot. But if you just need to move it around until you get more cash then it does release the front disc's.
I took the check valve out of the drum/drum master to get the disc brakes up front to "let go"
Now I a searching for a 1972 MANUAL master cylinder. That will bolt right up where the 67 master is. Not so easy so far.
Today I called around local, to see if there is two part numbers for a 1972 disc drum master cylinder. One for manual and one for booster set ups.
Can't seem to find the answer so I searched and am here now.
