Our notches are made to match the bends in the 67-72 chassis. You could try bending yours to match but it's going to be tricky to get all four of them to match. Plus you're top and inner pieces are flat cut straight, which you wount be able to bend to match the sides.
If you choose to send yours back and purchase ours you'd save yourself a ton of work, and in the end you'd have a much nice looking piece.
Here's some pictures images of that notch that I installed on a C10 with a set of our bag brackets as well.
You can find that notch on our website :
http://www.kplinks.com/product.php?p...3&cat=7&page=1
Good luck with your project.
Clint Petree
KP Components Inc.
866-KP-LINKS
www.kpcomponents.com