the material is the same, but the complexity/difficulty of the questions tends to be a little different. doing well in pre-clinical courses is an indicator that you have mastered the material on first-run, and that you should reach your potential faster than, say, somebody who blew off the first 2 years.
now, regarding what that potential correlates to in terms of score depends on several other factors (some of which are within your control [such as ability to correlate material from different subjects and your capacity to memorize large amount of information] and some of which are not [test-taking skills etc]), and the only way to get a sense is to take practice tests (mainly the NBMEs) which can give you an idea of the ball park of the score that you would get if you took Step 1 at that particular stage of your prep.