Mike,
I still don't know for sure if anyone has ever fit the ARB on a 96-99 pathy... What I assume will happen, is you will have a gap between the bumper and the grille, as the grille on the older R50's is flatter than that of the 99.5-04.
The TJM I have is made for the 96-99 pathy, and I have it on my 99.5.
It fit the mounts perfectly, the only issue I have is the grille covers more of the top of the bumper than it should, and I cannot access some of the holes for the winch. (and I had to remove antenna tab... hood sticks out more too.)
I know "Daddy Rim" bought an ARB Bumper to put on the older R50, but I never heard if he got it on, or how it fit -- you may want to PM him, and ask him how it went.
Also the subject has come up on the 4x4parts forum, but I don't recall for certain if anyone has done it. I think one guy put one on a QX4, and ended up with a gap... I'd suggest you search there, as I'm only going from memory, which is a scary thing. heheh