How can i keep my dogs from fighting over toys?

Your heeler and pit are high energy dogs that require more than just letting them amuse themselves with toys. (Wear them out with appropriate exercise before toy time.) Clearly there's a territorial and pack hierarchy issue developing, you need to let them work that out or the fights will become more aggressive, but you also must determine what their positions in the pack are and reinforce with proper handling so as not to confuse the situation...they are not all equal (they are dogs, not children) and they need to have you reinforce their positions properly to keep the peace.