The B-pillar lines up almost with the raised pads on the cargo floor. There are a few things that need to line up though and I'm sure there is are some nuances for each install (how many OEM parts vs. aftermarket):
- bolts that hold cab floor (not pictured in this shot) to bedside
- bolts that go up through the cargo floor to the capture nuts inside the bedside b-pillar post
- bolts that hold support panel to bedside and cargo floor
- bolts in torsion box end cap that connect cargo floor, bedside and support panel
Here is a better shot - older picture.
After building one of these up from scratch (on my 71 4x4 Blazer project) - I can see how these all rusted out in the B-pillar as there are several pockets for mud, etc. can hide and cause issues.