Wow, that's got to be the most assinine engineering example I've seen on any of the trackers/kicks if that's where they put the ABS sensor wheel.  Talk about overly complicating things.  That being the case I would guess you have two options. ÂÂ
If the outer diameter of the sensor wheel is being interfered with by the diameter of the new ring gear you're pretty much out of luck.  If it's something to do with the holes just not lining up you could probably get them drilled/machined out to get it to fit. I'm guessing It's probably that the inner diameter of the ring is too small to clear the ARB spool that's causing the problem though. You might be able to get that enlarged and fix the problem, doubt it would be too expensive if that's the case. If not, then you're going to have to live without ABS and that's about all there is to it.
If there's nothing that can be done, I'd just see if you can get away with pulling the ABS fuse out and ditching the light.  You probably don't want to have one axle of the vehicle using the ABS and the other one not, that's pretty much an accident waiting to happen.  If there's one part on the vehicle you don't want to be unpredictable it's the brakes.