I've wanted to do that for years, I think the TJ's rear rollbar design, while protective of rear-seat passengers, just looks funky. Since I replaced my rear seat with a storage box years ago, I don't need rear seat area protection.
I might be misunderstanding you, but the YJ mounts in the same relative areas as the TJ (I'm pretty sure).
The spreader bars go to the windshield frame, the vertical pillars (I don't know if these you're considering these to be A or B), but the vertical bars behind the driver and passenger front seat mount at the floor. Then the very rear bars mount on top of the fender well in the rear corners of the tub.
I was under the impression the TJ mounts almost the same other than bolt holes pushed around a bit. Again, I may be thinking of the wrong part when you say B pillar.
Now, even if the YJ does bolt up in the same general locations, I have no clue how much drilling/hole relocation would be necessary to actually get it bolted down.