Here is a pic of the firewall to sub frame strap. My '69 Z28 is a Norwood built first week of May (05A) with a U79 "Blue Light" AM/FM Stereo, 4-speaker system with the multiplex-amplifier, shown on page 445 of the AIM. I purchased the car with about 45K original miles and restored it. It had all (4) ground straps which I still have. I attempted to clean and reuse the straps but they did not clean up to like new condition so I replaced them. The capacitor (fan blower noise suppressor) in the picture is detail #2 shown on page 439. Note that it states “ALL EXCEPT C60” for air conditioning and includes the body to frame ground strap.
I also included a picture of the Inner Fender Well (skirt) to Frame strap shown for an L-6 engine car on page 441. My car is obviously a V-8 car but it did originally include all (4) ground straps. The "E" head screw with star lock washer was on the strap in frame position so I reused it. All the other screws that go into sheet metal are replacements offered by AMK, #B-11099, 1/4-14 x 5/8” screws, Zink plated with a "D" mark. These are the #9420415 called out in the AIM. Note that the screws that go into the frame are #9420152. I can not be sure if the “E” mark screw I have is original.
Does anyone have an original U79 Radio car build about the same time period as mine with the original ground strap screws still in place in the frame positions? Are they like the “E” head screw? I would love to see a picture!