No such thing. Scores are going to be on the same scale. Supposedly, most, if not all of the questions eliminated are going to be the experimental, field test questions, so there should be no effect on the number or difficulty of the questions that are actually going to count.
There is no conversion because there will simply be proportionately less questions and less time for each section, but there is no way to know which questions to eliminate on a sample test, so you can't just not answer the last 11 questions, stop 14 minutes early, and apply a formula to convert your score. You still have to plow through each section on the sample to get your score, which should approximate what you will get on the real deal, even though the shortened test will have 11 less questions per section (other than CARS, which will have 5 less questions), and each of which will end 14 minutes (9 minutes for CARS).