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A Supra is probably the best car of its era for long-distance drives. It's also super-reliable. I did tens of thousands in mine with 600bhp and nothing went wrong. Just routine servicing items, really. That's after it was set up by a team of real experts, though. You want to find a car that hasn't been buggered about with by a cowboy.
Turbos - if you don't push high boost - can last up to 300,000 miles in some cases.
The rest of your questions can be answered using the search function at the top of the page, and that's going to become your very best friend because there is more information on this site than pretty much anywhere else on the web
It would definitely be worth paying the £10 for full membership for a year if you're serious about buying. You'll get access to the classifieds section where all the best cars are advertised and all of the technical help and buying guides you'll need. Plus, you'll find out which traders are in the Midlands