Wow! What a mess! This photo is looking forward at the B post with the left rear fender removed. By the time I saw this I'd already invested a lot of time. Too late to go back now. When first starting this project, B post repair wasn't even planned. However
separating them from the sills showed the lower sections to be quite heavily rust damaged. The damage was most severe where the B post joined the outer sill.
The backs of the B posts were just too far gone to patch and should be replaced. At the very top were rust holes allowing water to enter the interior of the post. The bottoms were completely holed where they joined what was left of the sills. These holes allowed even more water to enter the area rusting the sills and even the floors.