Complex sentence: The R40s were originally numbered numbered 4150-4249 and 4350-4449; in 1970, cars 4350-4449 were renumbered to 4250-4349.
Split into simpler sentences: The R40s were originally numbered numbered 4150-4249 and 4350-4449. In 1970, cars 4350-4449 were renumbered to 4250-4349.