I have a 1968 AMX 390 4 speed with front disc brakes. I recently replaced the rear drum wheel cylinders (one was leaking a bit) and when trying to bleed them I wasn't getting any fluid to either cylinder. Disconnected at master cylinder and was getting fluid so moved to what I believe is a proportioning valve where after disconnecting the input line was able to finally get some fluid to the rear cylinders, albeit not as much as anticipated. Was wondering if I should replace that proportioning valve but am having trouble finding one even listed. I see them for disc brake retrofit kits but not as a standard equipment replacement. Can anyone tell me if a production 1968 AMX should have a proportioning valve or is that just a tee? Thanks in advance.