Ide like to buy perhaps some brembo brakes.
Where can i go to convert my ef9 to have rear brakes?

 

What kind of Brembo's? Blanks are a very good decision and able to withstand a ton of abuse. Rear disc swaps are fairly abundant, I think you can pick them up at password jdm, or weaksauce, look in the FAQ in the Civic forum to find more info- there's a bunch of it there.

 

junkyard!
Buy your disc set up (any 90-2001 Integra, 90-91 CRX Si, 92-2000 Civic or 93-97 Del Sol with rear discs will work)
E-brake cables from a 90-91 CRX Si
4040 prop valve if you upgrade the fronts too or a 2040 CRX Si prop valve if you are keeping your stock front calipers

and throw new rotors on too! brembo blanks are nice for the price!

 

and these are the part #'s for the e brake cables for a crx si...
most likely you won't find the cables at a junkyard unless it still has rear brakes

they are like 65 bucks each last time i checked

47560-SH2-931
47510-SH2-931