The Progress Rail PR43C is a 4,300 hp (3,210 kW) C-C genset diesel-electric locomotive built by Progress Rail Services Corporation. It is the result of a conversion of existing EMD SD50 locomotives. This involves replacing the original EMD 645 prime mover with a pair of Caterpillar engines, a 3,600 hp (2,680 kW) C175 engine and a 700 hp (522 kW) C18 engine. The locomotive was jointly designed by Progress Rail and Norfolk Southern Railway.