anybody ever use Dr. Diffs ring and pinions?

I'm about to get the rear put back in my car so I thought I would derail that by considering putting a 3:55 in it to replace the 3:23. I kinda want to do this once and be done with it. Everything is new Mopar or Timken so all I would have to do at this point is swap the gearset and set it up. I have a 742 suregrip center which leaves me with limited choices as far as makers go but I noticed Dr. Differential has a good price and was wondering if anybody had any experience with his stuff or knew who makes them for him. Thanks for any responses.