I have da rear disc I'm putting on my 91 si hatch. I eventually plan on putting da knuckles and brakes on front or doing the fastbrakes 11" rotors and getting da dc calipers and going that way. Reason for asking is either booster is bad or mc is bad and I figured if replacing with new why not change it out for a better setup now than original and switch it in year or so

 

You need to keep them pair so if it is a 260v (non abs) then you need to get the same booster and mc. If it is 290v (ABS) then you need to keep the booster and MC the same too.

 

okay i wasnt sure if i put the da mc and booster in car with factory civic si calipers if that would be too much brake for the smaller calipers and rotors in front