As far as I know there’s no internal connection for roof rack mounting. You can invent something and use the side channels to mount to your roof rack, also I know a lot of folks just simply drill the bottom and use a a sealed washer and bolt down to their roof rack which is my second choice.
I’m thinking to sell my D2, it’s a 2003 special Kalahari edition with 2” life Fox shocks. 5 brand new BFG MK2. Let me know if you’re still looking or interested.
Here’s more about Kalahari Edition they only built 150 of them.