Thanks to a heads-up from Cadence H., I found GMTX SD60 #9014 trailing on Norfolk Southern train 12R stopped at Success on the H-line north of Front Royal, Virginia. Pics:
NS D9-44CW #9398 leads train 12R north near Cedarville, Virginia on 10/06/2018.
GMTX SD60 #9014 trails on NS train 12R on 10/06/2018.