I guess I'd focus on the Females, who tend to have the smaller fangs and horns and stuff. The details on the males can be fixed later. Worry mostly about the ones with significant differences.
Actually I'll add this to the thread too.
Pretty much all of them, because in the index they are 2 seperate sprites front and back which means if someone only did the male or female version than the one they don't edit wouldn't have a opposite gender counterpart so if you planned on putting them in a hack you'd either have to get rid of the gender differences or leave the one not sprited as is which would look odd if you were changing it's type