I have an fg637,ex army,so came with body. Some observations...
1. Needed turbo, allow about 5k if u outsource the job. They respond well to turbo and many have been done successfully.
2. As Dan mentioned, electronic issues are minimal or nil. My mechanic, who does Fg canters for a Fraser Island tour company, rates the older models for reliability and identified the fg637 as one he'd take to more remote areas.
3. We have friends with later model trucks, while they are not reporting major issues, there is little, if any difference between trucks as far as comfort and driveability goes, they all need suspension, wheel and tyre modifications to make them acceptable and to perform better. Naturally,newer models have better engine performance at the cost of complexity.
4. With wheels and tyres, the older models atm don't have certification from say Kym Boltons TruckSuper Singles, so depending on where you are, theres a chance you will need to get private certification through an engineer to make things legal. Newer vehicles have had the tick,so essentially just paperwork to get those approved. ATWs cover older models but I don't recommend the 19.5s over the 17s from Kym due to cost,availability of tyres and comfort and performance differences, so go with 17s if you can.
5. Ours had 24k 4 years ago and now has 65k without a blip. It had been serviced within an inch of its life. I assume Fire vehickes are the same. The only problem ,if it is one, could be if used as a stationary engine meaning the odo isn't mkving but the engine is doing work and perhaps brakes which aren't getting much of a workout corroding the cylinders or something which is a relatively mi or issue to rectify.
