A pre-match is only available to DO students and ECFMG registered students (FMGs and IMGS).
Its when a residency program decides that they want you and offer you a contract or state in writing that they are going to rank you to match so that you must do the same in your rank order list.
Basically, you go through the match process just like any other students, us or not. If a program wants you they might offer you a spot then and there. Most often they wait towards teh end when they see who they really want at the end of teh season and decide whether to offer them or not.
It has nothing to do with scores or certain schools. Its just a matter of whether a program offers them and if they are willing to offer it to you.