The venerable SD50

[CSX5202]

From my research on the SD50, it would appear that the 645E3 could have been further refined in order to produce more horsepower. But, could the SD60 still be considered an SD50 with an EMD 710? And can someone explain what NS and CSX are doing to there SD50's? And could they ever replace the prime mover with a 710G? Or personally, could they (if they wanted to) drop in the 265H?

[BNSFdude]

The 645 WAS made to have more horsepower. Thats where the F block in the 50 series came to play. It was a flop. The crankshafts didnt like handling 500 more horsepower and the higher RPM that came with it. Many 50s were derated as you know back down to 3000 HP and 900 RPM tops.