What is this called?

[RAVEN]

Long time digging out that information Alan.
This part has no action of being a seal in its location, as it mounted to the underside of the cross frame of the upper rad support, and had no soft rubber seal to mate with any other part.
The only seals that existed around the rad opening was the triangler units on the sides of the frame, as Alan explained.
There was a seal across the underside of the hood and it mated to the top of the fan shroud where it was bolted to the upper rad support. Again Alan explained this, and it needs to be known that this seal/flap varied from year to year for 64/65 and 66. due to the changes in the hood shape
There were many gaps around the rad, so to have the questioned part being a seal is misleading, it simply was a piece of plastic to lay the wires that traversed across the upper rad support from one side of the car to the other, and prevent the wires to just be left exposed.

[Alan H. Tast]

Raven, thanks and happy Boxing Day, eh? Since I don't have access to a 64-65-66 in my birdhouse, if someone could post photos of how the side seals/deflectors are shaped and mounted, especially the right side difference between early-late 66 vs 64-65s, along with the underside of the two conditions present for '66 (with and without A/C), that may help others understand what's used to seal off the radiator opening.

As for the wiring shield, same thing. The disconnect between the illustrations and text in parts catalogs don't help for this, but a few more in-place photos may.

And, full disclosure, I put the effort into trying to document and help solve this "mystery" in part to develop this into a tech article for the Scoop and provide another data point for VTCI's 1964-66 Original Factory Specifications (OFS) revision. I'm sure there's more than a few people wondering how seals and wiring retainers were used.

[travellew]

Holy crap you guys are rockstars.. No wonder I couldn't find it! I tried every version of "seal " I could think of, but its not a seal. Now that makes much more sense!

I have removed all my seals in the engine bay at this point, but I could probably put them back together and take a picture. My car is a non AC version so that will be a picture of one version!