I suggest you communicate directly with the pain fellowship director to find out what type of research they are doing. For example, at UCSD, Dr. Tony Yaksh is doing basic research dealing with pain mechanisms versus say at the University of Washington, psychological aspects of pain behavior may be the strength of their research. Also, take a look at some of the pain journals e.g. Clinical Journal of Pain, Regional Anesthesia, Anesthesiology, Anesthesia and Analgesia (pain sections), the American Pain Society journal (don't remember what it is called). Look at the research, the authors, and the institutions they are from. This can lead you into the right pain fellowship (clinical or research). Hope this helps.