I am working on a 73 240z that has been in the shed for over a decade. Cleaning and clearing brake lines and replacing calipers, cylinders all hoses and master cylinder. The proportioning valve appears to be a 260z type (4 lines) and was not allowing fluid to pass through to the rear line. Disassembled and cleaned (parts looked okay but were really gummed up) but still no go. I see some similar appearing valves on the internet listed for 280ZX but wondering if they will work?