+1 on the Volvo suggestion. Early 90s were very safe, still relatively light (hood and liftgate were aluminum) and they were reliable as anything. Airbags, crumple zones, stiffened rockers. Oh, and if you want to put a different drivetrain in, it's been done to death so you'll find plenty of info. 940 had better cd than 740 due to redesigned fenders, bumpers, and I think maybe even windscreen angle. There will be aero pieces available, too. No six speeds if you stick with the stock 2.3...only 5-spds, unless you fab up your own.
All that said, the old man gets 31mpg from his house in NJ to my place in central PA and never under 26 mixed in his 95 Caprice, 5.7LT1 but it's the towing package...2.41 or 2.73 rear, slightly tuned LT1 but not crazy. Nothing else fancy other than lack of a lead foot. It drops a bit when I drive it.
