you dont need that sh!t for 31s. but I think its some kind of oring removal..search pirate. I am sure its been done 100000000000000000000000 times. Just run the 8.25/d30combo. anything else for 33s or less is a waste of money IMHO.
The mod that I did and most are doing is a prop valve mod when changing over from drums to disc. Not sure on th MJ but here is a link for the newer jeeps may apply to yours just not sure.
Get a brake booster set up from a 97+ Xj. You can also get a proportioning valve from a ZJ with rear disks, IF you need it. Most don't even go that far.