I've searched around the forums and all similar questions seem to be asking about the full exhaust, not just the muffler.

 

What exactly are the ed7 and da6?
90 crx and 90 integra?

I'm just guessing because I've seen these two, and they do look very similar.
You're right, the mid sections will be different. You want just the axle back.

Search on autozone or something similar and cross check the part numbers.

 

Yeah the ed7 is a 91 civic si, and the da6 is a 91 integra x-si. I'll go ahead and look at autozone to see. Thanks