My 89 Civic si has change the 91 integra RS front and rear brake. I am just wondering the integra's brake master cyclinder and buster are perfect fit to put it on into my 89 civic? Thanks!

 

I had to change one of the fittings. Just chopped of the crx line and then put fitting from the integra and flared the line. Piece of cake. You should look into getting a Proportioning Valve from a car that had rear discs. I think they were different.

 

you can use the 90-93 Integra master cylinder and brake booster.