 At the SCL merger, it was assigned number 600 and then later received SCL number 1950.Louisville & Nashville's four SDP35s (1700–1703), ordered in spring 1964 to replace aging E and F units in passenger service, were completed and delivered without steam generation equipment installed, after approval of several passenger train cancellations from government regulatory agencies during the locomotives' assembly, leaving L&N with a surplus of passenger locomotives.After delivery L&N assigned the SDP35s to general freight service, installing radio control locomotive equipment in the steam generator compartment and using the engines in locotrol service until 1969.