I have run across bottom trim pieces that have three slotted holes and some that have four slotted holes. Was this difference a production year thing or a challenger/cuda thing. Both trim pieces appear to be very close in size but the slots are different. Some slots run horizontally and some run vertically. Can anyone help? In the picture, the red circle on top denotes the slot, and on the bottom, where the slot should be.

Thanks

I would like to know what the difference is too.I have a bunch of both types.

Are you sure they are all E-body.
70-74 E-body has this raised area and 71 up B-body is a bit different.
Both are the same length.

71-up B-body may be a bit wider in height and has a different center cutout shown here.
Poor picture but you may be able to check yours to this.

Yes, these are definitely E body pieces. I have a couple of B body trim pieces that I compared to. The B pieces are noticeably wider.