69:18 for , 67:19 for and 66:20 for . The SD50 was also available with wheels. The SD50 was also available with either HT-C trucks (identified with a hydraulic shock on the side of the middle axle of each truck) or the earlier Flexicoil trucks. Some investigators implicated the HT-C truck in derailments of Amtrak's SDP40Fs, so Conrail chose the Flexicoil C trucks for their SD40-2s and their first order of SD50s—the only customer to do so. The controversy surrounding the HT-C truck was eventually disproved, and Conrail chose HT-C trucks for their second order of SD50s and SD60s. SD50S The SD50S ("short frame") were prototype units built in December 1980. They were shorter than production locomotives by approximately . There were six SD50Ss built, all of which were sold to the Norfolk & Western and eventually passed to Norfolk Southern. They were withdrawn in the early 2000s as non-standard. Two were rebuilt in 2008 as "SD40E" models by Norfolk Southern's Juniata Shops, along with several standard length SD50s. The SD50S designation was also used for five locomotives built by EMD Australian licensee Clyde Engineering, Adelaide for Hamersley Iron. Shorter than production SD50s, they were equipped with a special double cab roof for insulation against the hot Australian desert sun in the Pilbara region. Withdrawn in November 1995, they were sold to National Railway Equipment Company and exported to the United States in February 1999 and used in national lease service. They were subsequently sold to the Utah Railway in June 2001. In June 2017, 6063 and 6064 were sold to the Chicago, Fort Wayne & Eastern Railroad, 6064 was relocated by Genesee & Wyoming to the Indiana & Ohio Railway and renumbered 5017. SD50F The SD50F was a Canadian cowl unit version equipped with a "Draper taper" (inset section aft of cab for limited rear visibility). Sixty were built for the Canadian National Railway as road numbers 5400–5459. Early engine problems resulted in a temporary down-rating to . Eventually the units were re-rated to ; however, like their U.S. cousins, they continued to suffer from relatively low reliability, frequently suffering engine, power assembly, and crankshaft failures. Original owners Rebuilds A number of SD50s have been rebuilt into the equivalent of SD40-2s. The Dash 2 features are already contained within the SD50. The units are derated from at 950 rpm to at 900 rpm. This is actually a quite simple