Well, of course it's going to be expensive. I think most people use CRV rear ends... Also, the Integra/Civic was never designed to be rear drive. It would probably be really awkward. Although, if you were into showing your car or whatever it might be cool. ANyway, probably not at all practical for street use. Just get a factor rear drive.
IMHO, I think it's not worth it because you'll just lose more horsepower during it's drive-train, and it'll weight more. If you go RWD, you should be puttin down some serious horsepower. If not, it's a waste of money. Like i said, just my opinion.