There are several companies that engineer such seats, and also provide engineering certificates for those adjustments, for Vic Roads registration. I don't know about the cost though, nor do I know what those companies are. Some of them design seats for disabled passengers, perhaps thats some place to start looking.

I have a 132kW Crewvan (5 seats) that has heaps of guts, and while not 4motion, has been more than adequate on the 4WD trails I've driven on while setting up Rogaines.