When asking about anything electrical on an 850, it's most helpful to others for you to state the country, year & body style of your car, because there ARE differences among the variants.
That said, the 850 Sedan, Special, Coupe & Sport Coupe use a 4-wire wiper motor, & the 850 Spiders & 850 Racers use a 5-wire wiper motor. Only the 850 Spider & Racer models have a wiper speed rheostat & a foot-operated quick-spritz/wipe switch unit.
New 4 wire motors are availabe from ALKO (Spain), Meat & Doria (italian company, source of motor unknown. as well as Marelli also source unknown. Does anyone have any experience wiht ALKO and M&D parts?