Fireshawn,
I have the same issue with my 84" Cat II finish mower with Cat I tractor.
I found an unexpected way to fix this. A QuickHitch! I picked up a Cat I quickhitch from TSC and the lower arm pins it wants are about much larger than Cat I. They supply bushings with it to go over the Cat I to adapt for the hitch.
I visited my local machine shop buddy and have him machining a pair of pins that are smaller diameter for the Cat II mower on one side, then larger diameter for the hitch. About the same as someone posted above, but longer on the inside.
The width of Cat I and Cat II are different, too. I had him make the pins about 4"-5" longer so they extend to the inside of the existing pins.
I should be picking them up Friday afternoon. I will take a picture and give dimensions if anyone is interested.
I should mention that the top pin on the mower is on a loosely movable section about 8" or so. It came this way. This allows the pin to lower to the top hook on the quickhitch, but I have to find a way to hold it in the right place. I haven't worked a happy solution for this yet...
Anyway, hope this helps, or gives you some ideas. As I stated, I am in the middle of this and will post pics when it is done.
-JC