Why is an 1992 80 Series LandCruiser rated at 2500 kg for towing purposes, and after 1996 is rated at 3500 kg? I know there's a difference with the valves, but they're basically the same vehicle. Is it possible to increase the towing rating (legally) of a 1992 model 80 Series? This question has been puzzling me and I would really appreciate knowing the answer.
There are numerous things that go into determining the towing rating of a vehicle, the valves not being one of them. It would be illegal to try and uprate the towing capacity of the 1992 model, your insurance company would certainly be unhappy about it.