Part numbers for the system as found on all RS cars, and CE1 equipped open headlight vehicles:
Wiper motor: GM 5045605 (stamped on end cap of motor and sliver tag as seen in pic. Tag is dated.)
Valve assembly: GM 4919508 (ink stamp on side of solenoid, as seen in pic, dated)
Service parts:
Solenoid coil: GM 4919674 (box stamped only, manufacturer's part number is stamped on coil bracket, see pic)
Valve assembly: GM 4919676 (valve only, discontinued eons ago)
Check valve "T": GM 4919503 (no pic, I forgot to shoot it)
I've pictured the parts that comprise the valve, pretty simple - two valve halves (upper and lower), internal needle and spring, "O" ring gasket, and the screw that holds the coil to the valve body. Most all of the OE valves existing today either have broken the bottom of the lower valve off (very fragile), which then will allow the needle and spring to fall out and disappear. Best bet is to buy a reproduction valve assembly, and either replace the original, or mount the new valve to a replacement motor. Wiring harness is available, valve is available, hose kits and nozzles are available; with a little expenditure and effort you can restore to the level you need.
Regards,
Steve