My '65 has the same knob pullout and twist for fan speed control . But I don't remember there being a lever under the hood ? I have replaced my heater core in the past and have had the entire heater box out and I truly don't remember any lever ? But it has been a while and my old memory fails me at times ?

" The heart of the wise inclines to the right , but the heart of the fool to the left " - Ecclesiastes 10:2