Well, these MT753's are the closest thing I can find to a half decent mud or AT tyre without going to the 27" range which I think will suck a bit to much grunt out of the EA81.

I have been quoted $195 each off a seller on Trademe which sounds reasonable.
Problem is they are only available in 14" rim.
So I had a good hunt around for a suitable 14x6 steel whitespoke with a Subaru stud pattern. But you just can't buy them.
So all I can think of is buying these,
http://www.trademe.co.nz/Browse/Listing.aspx?id=729367950Then converting the hubs to 140mm x 4 PCD to 139.7mm x 6 PCD
The deal is, knock two of the existing studs out, bolt the wheel on, mark then drill out the extra four holes, whack in extra studs, hub back on. Conversion done
I'm picking that 0.3mm difference wouldn't put bugger all stress on the two original studs...