Blacktopper and I changed over his K9 to Pitbull handlebars. The difference was just over 3" additional pullback. You could search Blacktoppers thread on that topic (handlebar conversion) and find the list of parts available from Derek/Donna, and procedural description of the project.
I'm not sure about the additional setback on a R'back...Roger remembers everything, so maybe you should pm him to see if he can tell you how much additional pullback Pitbull bars would effect on a Ridgeback as opposed to his K9, because he has owned both models.