I own a couple of old TAMD 60Bs. Parts are available but unless you are JP Getty or Bill Gates you do not want to call Volvo. Example: FSO solenoid from Volvo $1000 US or knockoff FSO solenoid on Fleabay $60.
Search the part # and Engine model on Fleabay. Lots of knock off parts are available. Buy one. If it fits and works then buy a spare.
BTW, I'm in the process of repowering to Cummins.
Family Motto: If you aren't scared, you're not having fun!