The three vehicles shown here:
DIESEL GAS AUSTRALIA were done here in Sydney by Diesel Gas Technologies aka KLR Automotive (not DGA). I've driven a couple of them. They did use the DGA system.
DGT stopped using DGA systems and, with Modern Motors in Dungog, developed their own more sophisticated system called Gastek Sequent II. I believe Modern Motors does most of the 4WD side of the diesel gas business them and they will know who does them elsewhere in Oz. DGT do commercial installations and some 4WD installs.
The guys from Modern Motors are on this forum (as they are LR specialists) or call Murray Rumble and ask him.