Sorry to be weighing in to this discussion a bit late, but the Glenfarclas 8yo is basically the age-statement replacement for what used to be labelled the Glenfarclas Heritage.
THe Heritage bottling was originally produced for the French Market. It was sold in a red square tin, and had french writing and tasting notes on the packaging. For some strange reason, quite a few Heritage bottles ended up in Australia, and could be found at unusual liquor stores. (I picked my bottle up at David Jones in the city!!)
Anyway, the Heritage was a no-age statement bottling, but I received word that it was a young whisky in the 7-8 year old range. It's my understanding that the Heritage evolved into what is now the 8yo.
(Alternatively, the 8yo could simply be the same as Heritage, but just badged differently for different markets).