The very first 110's were offered FWH's as a factory option but that was because they were part-time 4WD.
There was a firm selling FWH's for later 90/110's (a French firm I believe) saying that they saved fuel & transmission wear etc but I haven't seen their adverts for some years now. To be perfectly honest the 90/110 was designed for perm 4WD operation and I can't really see any real benefit of doing anything to change this (what were you hoping to achive?).
You could look through some back issues of LRO or LRE (I think you would need to go back at least 4-5 years) and then try contacting the people who made them.
With reference to the above post, it would as long as you locked the centre diff.