Has anyone else had a problem with the piece of plastic trim at the bottom of the grill on a 73 challenger? I'm refering to the flexible plastic piece that is shaped like a T when you look at it from the end. Mine appears to have shrunk almost two inches in length. It is about one inch short on each side where it is supposed to meet the flexible bezels under the headlights?Is there a way to stretch it back out?

Yes, they always shrink. I think someone might make these new in a set. They are called bumper fillers.

There is about a 1/2" or so slop on that fit.
I suspect it is because that filler piece was never changed from the 72 models. Factory oversight.
There is a difference on the fiberglass nose piece between a 72 and a 73-74. The mounting holes for the filler are different, as well as the width of the notch where the bumper brackets go. I have am de a 72 nose piece work with a 74 filler by enlarging the width of the notch, and drilling 2 extra holes to mount the filler.
All the fillers look the same regardless.

Correct me if I'm wrong here. The 72 Challengers had flush bumpers like the 70 & 71's. There were no bumper filler pieces on the front. The rear also didn't have the flexible fillers either, although it did have a narrow 70-71 style metal filler strip.

To satisfy the new federal bumper regulations for 73, the bumper brackets were extended outward.
Three flexible bumper filler pieces were added, and the huge chrome and rubber bumper guards added, along with a heavy steel re-inforcement bar behind the bumper. 74's were the same.

When I restored my 73, I purposely made mine look like a 72 by using the shorter 70-72 style bumper brackets. This made the bumper mount flush, eliminating the filler pieces, re-inforcement bar, and huge guards.

318..that is correct.
However, if you look closely at a 72 nose piece, there are the bolt holes for a (long #10 bolts ?)trim filler piece. Although the trim wasn't used.
The 73-74 filler pieces will not fit a 72 nose piece, unless you drill a couple extra bolt holes, and widen the bumper bracket notch.
Why the 72 nose piece had provisions for trim is a question.

OK, now I understand. Thanks for the clarification...

I got rid of my fillers on my '74...drilled new holes in the front brackets and bought early model rear brackets. Looks a whole lot better now with the bumpers up tight against the body.