Okay, the 95-98 ARC Explorers have two height sensors, the 99-01 option has one.
The rear sensor is mounted between the differential housing(right of center), and above on the frame cross member.
The front sensor on 95-98 models is at the left front wheel, between the lower control arm(rear side) and the frame(near brake line).
I installed the 98 system into my 99, minus the front height sensor and lines, front shocks. I bought a 99-01 ARC module to operate just my rear system. The odd thing is that most of the 1999-2001 ARC parts, I believe that all of them will have 1998 or older part numbers. Parts references also show the 99-01 system as not different, they refer to the years wrong. Ford ARC Explorer parts numbers and their application references are also wrong(years and part numbers).
BTW, many leaks can be fixed by replacing the plastic lines, those are the weakest links, moving and vibrating etc. Before I decided on using only the rear system, I bought the front crossover lines.
Basically the 95-01 system has three part numbers to cover the lines, front middle and rear. Regards,