Which B50 do you want to clone? Ampeg B50R, Sundown B50, Acoustic AB50, or...??? Bass amp kits aren't something I've seen too many of, especially solid state ones. Same with bass preamps, although I know of a handful. I don't pay much attention to pedals though, may be some more in that format. Someone posted a thread several years ago on TB about cloning the Ampeg B50R preamp section, can't remember if he ever actually made it happen though.