Ohlins makes a very nice shock with a remote reservoir and full adjustability. Comes with an extra spring for heavy load applications. Martin Paetzold reckons around R12k

Then Hyperpro imported by DMD (Linex) has a replacement fork spring and 2 shock options on their catalogue. I'm waiting for pricing. Will give Hilton Hayward a ring to see what he can do as well.
Once the boing boing is sorted it will be a mountain goat, very chuffed with mine.