Heat in my Z28

Ok bare with me here,,its my first ever restoration... This car is a 79 Z28 that originally had AC. I dont intend on replacing the AC but I do want heat and defrost. The picture below is of my firewall as it sits (except its in primer now). Correct me if I am wrong but the two metal lines comming out on the left are for the Heater Core? the Square hole is for the AC and can be plugged/covered? and the round hole at the far left is for the blower motor? There should be a plastic housing I will need to instal the blower motor,,,,and if I am correct so far,,,will that housing also cover the square AC hole?http://www.clubhotrod.com/photopost/...080607-med.jpg