Heres why the rear lower quarters rust out..

All that stuff wouldn't be much of a problem if the drain plugs did not get blocked so that rain water didn't collect there. Also, they obviously went with the LOWEST bidder on trunk weatherstripping which allowed the rain water in anyway.
Agree! Look at the pick ups in the last 3 decades. They all rust out in the same areas. Box sitdes, cab corners, rockers etc. :BangHead::BangHead::BangHead::bs_flag: