It shows this available for a 99 100 series but may be a problem with the web site... Someone else called me and suggested this as an option and I'd never herd of this... Just thought I'd post here to see if it was in fact an option...
The powertrax units are not ideal for a vehicle like a 100 anyways, since the operation is pretty harsh.
Not to get off on a tangent, but I had a Powertrax in my 60 and it wasn't harsh at all, barely noticed it was there. I think the confusion on the 99 year is that the 80 series was still available in some markets and there is a Lockrite available for the 80.
Also a 60 is a much more harsh vehicle in general so its normal noises and quirks mask the lockers noises and quirks a bit.
Again, not my first hand experience. People who have never had them always say that they ratchet loudly and handle poorly. Everyone I know who drives with one thinks the complete opposite. Good friend's wife DDs their 80 with a standard Aussie in the rear end, no complaints.
Moot point in this section tho.