I definitely concur on the older Volvos being good, especially the 70s 240 shoebox types..
we have a 240 too, a 1987 240GL sedan in refrigerator white... wife is the original owner, it has about 400K miles on it, had never even had the valve cover off until we finally had to replace the camshaft seals earlier this year.
in its lifetime, its had the alternator, water pump (a couple times), radiator replaced, the AW70 transmission was rebuilt at about 300K miles, and... ummm... regular service (timing belts every 80K miles, brakes as needed, that kind of thing). Oh yeah, about 5 years ago I replaced a bunch of the rear suspension bushings and installed overload rear springs as we've used it for towing a hobiecat quite a lot.
oh yeah, its had its antenna mast replaced a couple times, hah hah (topic topic!)
this car survived my wife's daily driving habits for years, then a series of our babysitters, nannies, and au pairs used it, then I drove it for a few years, fixing it up again (radiator, stereo upgrade, full set of custom seat covers), then my son learned to drive in it, and ended up taking it to college for a year or so, now my daughter is taking it as her first car. the 300E 2.6 was offered to her, and she prefers the 240, its more 'hip' she says.
mechanically, the 740/940 is a continuation of the 240, with a TON of engineering improvements. better torque arm design for the rear end, better swing arm designs, better front control arms, bigger/better brakes (especially the turbos), much much better and more sane wiring, better ventilation and a/c, better seats. the 7/9s are only slightly larger than the 240 on the outside, but have significantly more room inside. they have the same B230F (or FT turbo) series "redblock" engines, the same AW series transmissions, the same Dana rear axles.