Have you done any patching before? If so where? You have a welder and can mig weld? Whenever I get ready to do ANYTHING, I check stovebolt and the internet. I have done lots of various repairs and patch panels. Doesn't matter, I always study for a long time before starting.
I always try to find David Welch from Brothers trucks. Good videos by a regular guy who is like you and I. I may watch other homemade youtubes. I do not watch the "Hollywood" guys like Kevin Tetz or Stacy David.
Here is a video from David Welch/Brothers that will help you. (third video)
David Welch started making videos at his house in CA. 20 years ago and Brothers picked him up.
The important parts of your repair are:
1. To understand the original structure that will hold the patch piece.
2. Cut very carefully and small areas at a time, to eat into/cut off small pieces to save the inter structure. Save it to look at and take pics and measure to see how to rebuilt it before you cut it off, or save it so as to leave it and use it to attach the new patch piece.
3. You can see in the video what pieces you will need to buy. You may only use a portion of the patch panel. You may need two patch panels. You may use a portion of a patch panel and make the rest.
4. Life is better if you buy a patch panel, already shaped.
5. You seem to have floor and kick panel rust. If some piece is flat, use a flat area off of a patch you don't need or a piece of sheet.
6. It's nice to build it back the way it was instead of inventing your own method/design.
7. Think about every cut really hard before you cut. Try to think on how you are going to provide the proper piece to weld or bolt it to.
8. You may get into cutting on the A pillar hinge post, so don't let truck sag or distort the door opening or fender mounting, etc.
Other folks here may have other/better advice.
