at around 62 mph the engine makes a high pitched sound.
High pitched sound at higher speeds on 1991 Volvo 240
Check the fan belt tension. A loose fan belt for the alternator or power steering usually shows up when starting the engine or operating the steering but you could have a loose belt. A cracked heat shield for the exhaust may also cause a noise under certain engine load/temperature conditions.
It sounds like your center support bearing on the drive shaft is bad. There is a two piece drive shaft and a bearing in the middle have that checked