It is best to consult the vehicle owner’s manual for the correct group size and minimum rating.
If this is not available, you can look up the vehicle make, model, and year in a battery application guide and note the recommended group size and rating given.
While there is no harm using a higher rated battery than specified for the vehicle, you should not use a battery with a rating lower than what the vehicle manufacturer recommends. In fact, for older vehicles, usinga higher rating will improve starting and generally provide longer battery life.