The older integra brakes will NOT fit on the crx. what u need to do is either find a 90-91 crx si with rear disc breaks and swap them off of there onto ur crx., or u could find some rear trailing arms from a 90-93 integra and swap the spindles off of the integra trailing arms and put them onto ur old trailing arms after u take ur drum spindles off. the whole trailing arm for the newer crx si will fit but the trailing arm from the integra will not fit becasue it is a 1/2 to long and thats why u would have to swap the spindles...
If u get a 87 and older civic/crx then those rear breaks from ur 87 integra will fit on those, but not on ur crx..