I used a 9" dual from Master Power Brakes. In full disclosure, I bought a 9" dual booster / master cylinder unit form MPB. The master cylinder was a dud - couldn't bleed the system so I purchased a Wagner to replace it. The booster failed a couple years later so it was replaced by a Tuff Stuff 2224NB 9" dual booster. I'm not sure if Tuff Stuff has booster mounting brackets, I used the MPB brackets. I can't recommend MPB stuff due to my experience.