Am I imagining this, or did I read somewhere that vans for Norway were the only ones fitted with dual circuit brakes?
It should only (!) be a matter of finding a generic dual circuit master cylinder with the correct bore and remote reservoir.
Mine only ever had single line brakesI've not done it but if the export vans have it fitted then it must be possible. I think the main problem would be getting hold of a suitable master cylinder, I wonder if the last Spacevans had them fitted.