brakes leaking from proportioning control valve

[Kisner]

Wish I could help you, but I don't what the 2 small holes are for. Not sure if it's rebuildable or not. I'd suspect a rubber seal has gone bad on the inside but even if you could take it apart might be hard to find the right size seal to replace it. If you haven't already, try Metro Mustang for an original used one. They have countless stangs they're continually parting out. The guy I always deal with is Tim. His e-mail is tim@metromustang.com or you can call him at 404-767-3378. During my restoration process, he had several items I couldn't buy anywhere else.