I found this info on an ABS repair specialist's website many many years ago, so while I believe it is probably correct, please confirm this yourself before acting upon it!
Quote..."Volvo has a habit of giving one part several different part numbers. I'll list them here".
All 96-98 FWD cars with TRACS - 850, V70, S70, C70.
All 96-98 FWD cars, without TRACS - 850, V70, S70, C70.
98 AWD cars - XC70, V70R AWD, V70 AWD, S70 AWD. (All these AWD cars have TRACS as standard)
99-2001 FWD with STC - V70, S70, C70, S80.
99-2001 FWD without STC or TRACS - V70, S70, C70, S80.
99-2000 AWD and FWD cars with TRACS - XC70, S70, V70.