Rebuild, WAY cheaper and you will get the same quality shock (rear).
If you read one of the latest modified shootouts in DirtWheels, they test Z400, Raptor, 400ex and I can't remember what else, but they put aftermarket shocks on all bikes, front and back, but kept the rear Honda stock because it was just as good as aftermarket.
This is from a mag. where money isn't an object in their testing, and they chose to stay stock on rear. That should say something.