Dirtygrunt:
It looks like you are making some good progress. I find that if I remove all the ugly stuff, it helps with the big picture.
As far as I know, there is no patch panel for the lower "B" pillar, however, some of the cab corners wrap all the way around, to meet the rocker, so they may cover most of the damaged area and get you close enough to custom fabricate some infill pieces. Before purchasing any replacement panels, make sure you talk to a customer service tech and ask them if the cab corners are specifically for the '60-'66 Chevy trucks and are the "full-wrap" style.
I have had good luck with:
www.lmctruck.com for floor pans & kick panels
www.classicparts.com for floor pans and rockers
wwwtruckandcarshop.com for all body panels
Keep us posted on your progress and before you know it, you will have all the bad gone and start bringing your cab back to life.
Inch by inch, life is a cinch.