The four U36B's that Conrail purchased in 1976 were originally built for Auto Train but never delivered due to Auto Train's financial difficulties at the time. The units were built to Seaboard Coast Line specs, complete with Blomberg trucks; however, at Conrail's request GE replaced these with AAR Type-B trucks. Conrail placed the locomotives into series 2971-2974.

The Seaboard Coast Line specs can be seen in the various details of the locomotives. Many of these details are unique among Conrail units: a firecracker antenna, a red and white signal light in the short hood, five chime horns, and an SCL-style rounded pilot. As time progressed, Conrail removed some of these SCL details: Sinclair antennas replaced the firecrackers, the rounded side cab windows were plated over, and the horns were replaced with other styles.