I am not really answering the question properly but i got a custom made bench seat put in the back c/w Lap belts and child restraint anchors cost me around $1100 aus including an engineering cert..............Dazz
I have a 72 fj40. I wanted a forward facing seat for my daughter. My friend gave me a rear seat from a jeep cj 7. It fit fine, although I added 2" spacers to the mounts to increase the height. I used 2, 5 point harnesses I ordered from a volkswagen dune buggy magazine. Got both with mounting hardware for under $100 US. She likes the forward seat much better than my other cruiser with side mount seats. Mr Bill....
RyRy Im in Perth as well .There is a few landcruiser seats for sale in this weeks Quokka out of hj75 PC that may fit. Central 4x4 in Balcatta has a cloth covered fj73 rear seat with headrests for sale.If the later model forward facing rear seats wont fit you could try the Suzukishop in Cannington . Last time I was there he had quite a few seats out of older suzis that looked good .Another place you could consider is the Lada wrecker in Malaga although you would have to fabricate some brackets to attach the lock mechanism when the seat is in the ready to use position
Considering the age of your vehicle your either going to have to spend time looking for originals most of which have long been discarded or do the conversion . If you manage to find a wrecker who has the originals they will want a high price for them . The suzuki are plentiful and cheap. I dont think it looks too hard. If you get the parts together as it says in the instructions you could then take it to a body builder or panel beater who can weld the fittings in .The money saved on seat purchase will offset the cost of installation.
I have seen GQ patrol 3rd row seats in the back of a SWB 40 - look good and fold down so you can still load stuff in the back. I think they have seatbelts mounted to the seat as well - lap only. As long as you don't have a roll cage, roll cage = 2seater... ADR's.
Pete the Nissan GQ PATROL is landcruisers main competitor. They come in swb and lwb wagons ,pickup, well body and tray top .Some were rebadged as a Ford Mavericks in Australia. I got told recently that they werent available in the US.Youve most likely seen them as the vehicles that were used by the UN in Iraq by the weapons inspectors. As with Landcruiser you can get the 3rd row seat option in the lwb wagon , which is more for little people.