You can make the stock petrol injectors work for Lpg, but the system isn't avaliable off the shelf for the price ($$$) most people want to pay.
If you want cutting edge, BRC (in cahoots with Impco) make a similar set-up. The Dutch and other Italians are making world class systems too.
You will be the pioneer in the system in Australia, as the earlier Vapour sequential injection were by Biophase/Liquiphase and Parnell in 1994-1995. Issues with saftey made them back out of full scale production.
Liquid propane injection is some way off, as the groundwork on safety has to be covered off in an increasingly litigation bound world.
Heck, we pump propane at 275 Kpa, and have done so for years, but the stepper pumps for fuel pressure regulation between empty and full are still not full proof.