There is no 'one answer fits all' here unless the answer is "*it depends*". Basically you'll have to determine what distance you'll need depending on the type of starter IN EVERY APPLICATION. There just are so many ways to retrofit a PG, so many different parts available (INCLUDING CONVERTER) you could list everything but still the answer is the same. On my Tilton the free gap was .100" plusminus .040 AND to set the backlash between .01 and .03"