sounds like youve got a mess with your brakes but i can answer a couple things. you can put a proportioning valve on any brake set up that you wont and you may or may not need it. you might need it to adj. front to rear brake bal. once you get all 4 wheels woking right. on the vac. deal most of the time if you dont have enough vac. you will have a hard full paddle. if youve got a drum brake mastercylender on the disc brakes tech. is right it wont hold enough fluid, so you need to fix that first