The two units in class DL39 are ex-Alco demonstrators 636-2 (#1280) & 636-3 (#1279), which were purchased from the Morristown & Erie Railroad after sitting dead for several years.

1279 (Exx Alco 636-3) couldn’t simply be repaired because it had suffered fatal freezing damage while being stored, so it was remanufactured with a Cummins QSK95 into a “C-644” (with almost no external changes; Alco’s big centuries have ample room to fit a QSK95 and the related emissions control apparatus, so the only obvious visual change was to remove the last two engine compartment doors and install one of ILW’s 3-panel air intakes) and then put into service on the Parsons Vale’s western lines.

1280 (exx Alco 636-2), despite not having fatal prime mover damage, took longer to put back into service because it was added to the queue for repairs, and only came out of the shops for shakedown in early 2023. It is currently running on the D&H/OSW/I&M’s Chicago mainline.