If you're going for durability, reliability, and ease of maintenance, you might want to consider something built on the Ford Panther platform (Lincoln Town Car, Mercury Grand Marquis, Ford Crown Victoria). Livery services, taxi operators, and police run these body-on-frame beasts for 400k+ miles in some of the most abusive environments imaginable. Some police departments actually stockpiled the Crown Victoria when it went out of production because they worried the replacement FWD Taurus wouldn't handle it.

They ride great and have lots of interior room. Performance parts are cheap available (many Mustangs came with the same engine) and junk yards are full of wrecked police cars that can donate parts to the cause - e.g. putting a Police Interceptor swaybar on a Lincoln Town Car.

The 4.6L 2-valve V8 is an American 'red block' and is hard to kill even if you're trying. The rest of the car is purported to be easy to work on. Many forums exist for support as well.

A Panther is a 180 degree departure from a Saab wagon - but it may tick your boxes for mechanical uniqueness (the only other body on frame car went out of production in 1996), dependability, durability, and ease of maintenance. Depreciation hits these cars like a ton of bricks, so you could get a good one for cheap.

A year-by-year guide to Panthers is below. If I could find a good one, I'd go with a 2003+ with side airbags and hydroformed frame rails.

http://www.thetruthaboutcars.com/2011/05/piston-slap-setting-the-record-straight-for-a-tall-and-solid-panther-man/