Wiring connections for johnn deeere 120 mower 3 wires going to top of mower deck I need polarity

Hi,
If this is one of the old 120s out of the 1960 - 70s, then it is likely that the deck has a model number tag on it that identifies it separately since they were purchased that way. Generally it would be probably a 47" though it could be an early 50" model. Neither are available anymore but one needs to know this for a credible answer.
Peace,
Clarke