Here are the body corner patch pieces that I was looking at. They are listed on AMD as "not for Charger or convertible".
http://www.autometaldirect.com/amd-deck-...ger-p-4709.html

"Maybe" cut a patch out of this deck filler panel.
http://www.autometaldirect.com/amd-deck-filler-panel-68-70-b-body-except-charger-p-1036.html

And use sections of these trunk gutters.
http://www.autometaldirect.com/amd-trunk-gutter-upper-lh-68-70-plymouth-b-body-p-2746.html

70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"