First, it's post-bac with no "h" (short for post-baccalaureate). The formal postbac schools tend to be helpful not only because they give you an opportunity to improve your credentials for medical school with additional science course work, but also because the program administrators serve as advisors to you and actually also go to various medical schools and somewhat effectively have be able to market their candidates. It's a very hands on program and they keep on top of you and make sure that you are doing everything you need to to succeed in your courses and get everything out on time. (Less formal postbacs leave this to you on your own - very laissez-faire). Some postbac programs have linkages with med schools, meaning that if you meet certain criteria you either get into or at least get an interview with a certain med school. The formal postbacs tend to carefully scrutinize candidates on admission to ensure that they have a high percentage of their class getting into med school. However, I think it is a mistake to have just a single med school in mind as your goal. Med school admission is competitive, and not everyone with the credentials gets into their dream school. In fact I would suspect most don't.