Merry Christmas everyone, 
For my birthday, my wife purchased me a 1975 280z:).  I am its fourth owner.  It has only 58,000 document miles ( I have all of the paperwork from the P.O.'s).  I have purchased an air dam for it (MSA Type II).  I searched the forum and looked at the instructions on how to mount it.  But I am not about to find the information needed.  Per the instructions from MSA, I am to remove the lower front valence.  Looking at the FSM I download, it does not mention a lower front valence.  Looking at the sections under "bumper and radiator grille - pg. BF-7, I see the items "front bumper sides".  Am I to remove those also?  If so, what does the air dam mount too?  I have removed the old bumper and its hardware.  I have included pictures.  Thanks in advance for your help.