REAR:
Firstly, from my communications with ARB it would seem that the "big ticket (ie big $$$)" items in the locking differentials are the splined sidegears. Tooling up for them and production is done by a third party and supplied to ARB. So it would seem it would be easier to get rear axles made to suit the splines that they have, in the nearest size differential that can be modified in other dimensions to carry our ring and pinion dimensions/offset (if that makes sense).

Be aware that we are not talking about just the sidegear (if you were hoping to just send them one for inclusion in the diff), there is a locking ring machined on the back of the one of the sidegears, that is used to lock against the hemisphere, so the tooling and production of that particular item is a very complex operation (hence the cost).

FRONT:
I can source a halfshaft over here, and what I will be doing this week is also sourcing a Suzuki halfshaft to see if it will fit int the Kia diff. If it does then we are halfway home <img src="/forums/images/graemlins/smile.gif" alt="" />