While some cars are known lemons and should be avoided at all costs, the vast majority of cars and utes are okay as second-hand buys provided they’ve been serviced and maintained properly. And that goes for all makes and models, not just the VW Amarok. The point being that a well-maintained Amarok might be fine with 200,000km on board, while a neglected one will be junk by the time it has covered half that distance.

That said, the current crop of modern turbo-diesel dual-cab utes are mostly tuned pretty highly which means that by 200,000km or so, many of them will be showing a bit of wear. This might be most apparent in the intake system, the turbocharger, emission systems, transmissions and many other hard-working parts. Again, it all depends on how they’ve been maintained and how they’ve been used. I’d be budgeting for at least some repairs on an Amarok with that many kilometres under its belt. At which point, of course, it all comes down to the purchase price.

The Amarok is rated to tow 3000 kg, which would make it marginal for your needs given that you want to tow around three tonnes. The Ranger and BT-50 are rated at 3500 kg, which would make them more suitable for you. The Ranger and the BT-50 are the same vehicle, it's only the features that separate them. For me, of those you list the Mazda is the best value-for-money.

I understand what you're trying to do, and the Amarok wheel might well fit, but I wouldn't recommend it. The Amarok wheels are 16 x 6.5-inch, the Q5's are 17 x 8-inch. Go to an Audi dealer, or a specialist mechanic and try to find a more suitable steel wheel.