Nice Ted. That unit caught my eye -- it's nearly 40 Years Old and still churning out the HP. It actually pre-dates Norfolk Southern by a few years, having been bought by predecessor road Southern Railway. This model (SD-40-2) was once one of the most common in the U.S., but after the passage of many years, have become something for fans to savor.
.... I thought Southern favored high hoods. Do you think the hood was changed during one of its rebuilds?
That is an interesting engine on lead. 7106 looks to me like a GP7 or GP9 with the short hood lopped off. What do you other railfan's think?