Have you considered going to a split system with a newer master cylinder? On my 59 truck the master was a solid lump of rust and I went with a newer system and plumbed the fronts and rears independent so if one side fails, I'd still have a bit of brakes like a modern car/truck. Might be a good time to do a bit of an upgrade.

\'59 Chevy 1-ton
'72 c-10 (in progress)
The Great Rust(less) Mountain
\'47 Jeep cj2a