The best long term fix is to mount a std junction box up in the hitch area and terminate the stub in it leaving enough to splice your new pigtail in the box color for color.
There is likely another box up there somewhere but removing panels is not the easiest way. Just another thing that makes you wonder if anyone ever thought it would need to be replaced.
Next time it will be a piece of cake.
2011 351RLTS Eagle, Mor/Ryde suspension & pin box
06 F350 Lariat PSD, SRW, LB, CC, EGR delete kit, 16K DrawTite hitch, Timbrens, TST TPMS
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