Sammy

Sounds like you are talking about the screws that hold the valence to the rear brackets.

Here is where things get ugly. Here is a picture of 70 cuda mounting brackets with the original screws firmly stuck in them. The have an overall length of 0.75" - top of screw head to the end of the screw. The washer is captured but lose.

Below you will see the reference listing that Dave Wise has for the top and bottom. He shows a screw with the washer being a formed part of the screw head. He lists 10-24 with a thread length of 0.625

Now it could be a difference between the two factories, but all my Challengers have had the lose washer type screw.

Hope this helps.