On my '67, the brake warning light stays on. The switch for the parking brake works fine. I believe the problem is in the distribution block. I removed the wire terminal from the block but nothing else comes out of the block. It looks like there is a valve in there that would move back & forth with a spring behind it but, it doesn't want to move. If it is stuck, is it somehow removable or do I need a new distribution block?

 

At one time, there was a leak and the valve moved internally to the axle leaking to stop the leak.
Generally, the fix is repair the leaks and open the bleeder to the opposite axle and press hard and fast on pedal.
This action should center the piston inside opening the electrical circuit.
The end of the indicator for the piston does stick out for visual inspection, about 1/4-5/16 inch, I believe. Pictures will show you the correct position.
If all else fails, replace and bleed system.

 

Does your brake pedal feel mushy or go close to the floor? Air in the system will trigger the light to go on.