There is 1 set of torsion box end caps (one per side) and then 3 other pieces of metal come together in the B-pillar.
The torsion box end caps tie into the pieces that Keith notes above. I did this work on a
previous project back in 2010 when many of the aftermarket sheet metal parts below were not available.
The B-pillar stuff is easy to see starting in
this post and then a bit more detail when I got the
other side here.
Parts List for a new blazer
solid windshield frame
69-72 Firewall (if needed)
Cowl Panel (if needed)
outer rockers (2)
cab floor (1) - will need tweaked for blazer use or
2wd version
blazer bed floor (1)
Step Up panel between floor and bed floor (1)
Rear Wheel Housings (2)
Bedsides (2)
tailgate (1)
doors (2)
Torsion Boxes (2)
torsion box end caps (2)
B-pillar support parts (2)
B-pillar reinforcement parts (2)
Blazer Body Mount and Bolt kit (1)
Nuts/Bolts - Grade 8 - Fastenal or Tractor Supply
Most of the links above are from one spot (Classic Heartbeat) - I have purchased from several vendors (GMS Pauls, Tabco, and several different resources AMD, Goodmark, Apex, etc.) so shop around for price, shipping and customer service that fits your needs. Since much of this stuff is oversize - you may want to consider a shop closer to home to save a bit. Several of the board vendors use the sheet metal they supply so they know about updates to molds, which parts will fit and which ones to avoid. Disclaimer - many, if not all, aftermarket sheet metal parts will need to be tweaked to fit perfect. Nothing I used fit perfectly the first time.
Let me know what questions you have along the way Mike. Happy to help in any way that I can.