I'm not a professional body man, but self taught. Thanks for the compliment.
Jim Carter Truck Parts is where I got quite a few of my sheet metal patch panels.
I found rocker panels at RockAuto. They have quite a few other parts as well.
With the exception of some parts that Jim Carter has made for them, most everything comes from the same (overseas) source.
Dynacorn is supposed to be the premier brand, but i suspect if you peeled their sticker off, you might find another underneath.
Good luck with your project. Feel free to ask questions if your run into a snag.