Old thread but I think the take away is category 2 lower link balls will not fit into a category 1 quick hitch.
Category 2 lower link balls are approximately 1 3/4" wide and category 1 lower link balls are approximately 1 3/8" wide.
If you have a category 1 quick hitch and an XR/MT LS tractor with the extendable lower links that are category 2 they are removable and can be replaced with category 1 extendable link ends. This mod allows the use of your category 1 quick hitch and is cheaper than the Pat's system and even moreso if you have a quick hitch already.
Note if your lower links are category 2 so is the implement side of the top link. That won't fit in the category 1 quick hitch either.