Considering that 20+ years after they were built they are still running with their original 5000hp 20 cylinder 710G prime movers, while the MK5000C's were rebuilt into SD50's, and the 6000hp GE and GM designs are all either retired or derated. Also remember that Conrail was going to order more SD80MAC's, but the split between CSX and NS cause that order to be canceled.
Stuart