Stripped down most of the front end and the diff today.
Diff had a 2.78 long bolt course spline centre. I salvaged the drums and brake components (almost new). The centre and housing are now in the for sale section along with my original 3.39 centre.
The front end was missing the brakes on the driver's side. Thanks to Rob I have a set of links to make the brakes work as this front end was shy as well. So I now have two front ends and still seem to be missing one "bolt".

I will search through my parts bin over the weekend. I trust that it was just thrown in the bucket by the previous owner when he stripped it down.
The front end also has a set of engine mounts welded in.

I compared it to my HR disck brake front end and the location is different.

So I guess it is not set up for a red six. Given the 2.78 ratio diff it could have possibly been set up for a V8.
Not sure what use it would be to anyone as I think any mod like that would now require a disc brake setup. Anyway if you have any idea of what it has been set up for or have a use for it - please let me know. My plan at this stage is to strip it down as spares so it takes up less room in the shed.