The cars usually came with a 904. Some H.D. cars like taxis and cop cars had 727s in them. My '81 Dodge pickup /6 has a 727 from the factory.
I hope this helps.
Its either a 727 or a 904. Go to the following link. http://www.mymopar.com/downloads/transguide.pdf
At the bottom of the page it shows both a 727 and 904. Note the different shapes of the pans.
904 most likely, 727 came on trucks and higher performance application (taxi etc.) but if it ca,e from a car it's most likely a 904 unless it's a stick??