is the master cylinder and porportion valves the same in the 99-00 Si and the 96-00 EX???

 

Nope.

 

Neither one are the same, but if you are doing a rear brake conversion on your 96-00 civic you will only need the proportioning valve from a 99-00 Si, forget about the master cylinder because there is not a lot of difference in the capacity of a 96-00 Civic EX and an Si prop valve. My suggestion is, only change out the master cylander(to a 94-01 integra MC) if you are getting larger front rotors and calipers.