I am wanting to get a Yukon Spartan locker for my 89 cherokee. They have either a 1.560" bore or a 1.625" bore. What does this mean and which one do i need for my Dana 35?

http://www.4wheelerssupply.com/catal...470_496_22_728

Here is a link to what i am talking about. Has anyone ran one of these before?

84 to 93 use the 1.56" and 94 to 01 use 1.625 in the Dana 35 rear.