I'm running the Boyer Bransden MK III on my 77' 750F, but it's never advanced correctly. I did get a little midrange boost, but that's probably just because my points were so bad when I switched. I'd go w/ the Dyna system if I had my money to spend over again. As far as which Dyna to get, I'm not qualified to say, but many of our members are running them, so hopefully they'll chime in w/ their experiences.
Jay in Philly