Those are just like the stock hook mounts, the only thing missing is the hardware, the 2 L brackets that secure the front of the bkts to the front x member and the bottom brackets..#15 in the above posted image. IIRC, there is a special nut on one side of the "frame" that goes into a large diameter hole. I found a set at the bone yard and got all the mounting hardware with them for $20 bucks. Didn't want hooks, so I made bars for some shackles and put them just outside the air dam. Grade 8 hardware with aircraft lock nuts used for the mount pionts and I cleaned up a couple of shackles I had laying around.
Volunteer, American Society of Military History. http://tankland.com/
Just got a 1989 YJ too!