I welded up all the holes in the vertical drop down surface on mine.
Below is a picture of my original (October 64).
The Dynacorn's are short like Bryan said, but at least for me, only a little, maybe 1/4" to 3/8 towards back by the valence. At the wheel opening, they were ok.
I replaced min while the 1/4's were still on so I could see just how short they were. If you look real close at the far left edge of the second picture, you can see where the 1/4 starts to stick below the drop off.