Hi Everyone-
Turns out there was a mix up with XDP (the supplier). DH called Bilstein directly and was told we needed the 4200 or 4600 series (going from memory here and not sure of the correct series number). I had called XDP and asked specifically what series I should be getting for our application and they sent us 5100's. So XDP arranged to send us the correct shocks and will accept the return of the used ones.
We rec'd great customer service support from both XDP and Bilstein. I always order from XDP and have never had a problem. But it's nice to know that both companies worked together and offered us a solution so we were not out the $400+ for the shocks. I think Bilstein really stepped up b/c they were the ones that authorized XDP to accept the used ones for a return. We could very easily be out $$$ b/c I have no record of the phone call where I was told the incorrect series number.