'finishing this thread out- I found a small engine repair shop that had a couple loops of scrap oil-tempered spring steel push-pull wire that did the trick. It slipped right into the sheath.
The only "tough" part was accessing the upside down screw that secured the end to the adjustment lever behind the dash control. In hindsight, I likely didn't need to even remove it, but I did so to get as straight a path as I could when I was threading the new wire in. The only other part that required caution was removing the retaining clip on the plastic adjustment arm that connects to the control lever on the console- that plastic is pretty brittle.
$5 and a good Ford conversation and I am good to go. I'll post back with the gauge diameter and working length for future reference.
EDIT: 18 gauge and 55" between the loops to secure the ends.
Sonoma County,CA
1982 F150 Flareside XLS
NP435 4x4
351W Motorcraft 2150