I am adding factory AC to a non AC 70 Chevelle while also converting to a SS gauge dash. I have new dash and engine compartment wiring harnesses that are correct for the AC setup. The problem is that I need the location to drill the hole in the firewall for the AC harness and grommet to power up the heater controller. I have the assembly manual and have looked but I do not see it referenced on page A10 for the firewall penetrations for option C60. I see it shown in the air conditioning section but no specific location shown. Can someone let me know where the dimple is? Thanks ahead of time.