7 1/4 rear diff question.

Summit has gear sets for the 7 1/4's. But there is a split on the carrier as far as ring gear ratios that will work on them, From my understanding if you have a 2.76 or numerically higher you can go to 3.?? If your a 2.56 or numerically lower you have to get a different carrier. I could be wrong this is what I was told by a place that sells gears.