This aircraft was the last of 61 Reims / Cessna 337 TBGs built. Spectrum Aircraft modified it by replacing the two piston engines with a single rear mounted Pratt & Whitney PT-6 turbo prop, lengthening the cabin ahead of the wing and a new extended cargo nose. Registered N15SA, the Spectrum SA-550 Spectrum-One first flew on February 1, 1983. Planned certification the following year did not happen and the aircraft was acquired by Basler Flight Services in 1992 who renamed it Basler Turbo 37. Further modifications increased the Max weight to 5,952 lb (2,700 kg), but no sales followed.