I assume this unit is from the initial batch of SDP40Fs from La Grange—beyond its fairly low number, it has the more complicated sheet metal work on the nose. (Later ones had a simplified design, with a flat section where the access door is located.)
The reason this locomotive is looking so marvelous—in Phase II paint—is that it has just come out of the Illinois Central Paducah shops after being refurbished. Too bad that the entire fleet of this model would be taken out of service later this very year or early the next due to a mysterious problem that caused it to derail with enough regularity that it was untenable.
The problem *may* have been due to large water tanks which were needed for the steam generator. (This locomotive was designed to haul legacy equipment that still used steam heat.) There's also a question about a newly designed truck. In any event there's never been a definitive reason for the issue. The engines would be returned to EMD which recycled some components in the manufacture of the F40PH for Amtrak; some of the units were reworked into freight locos that ran for the ATSF.
Two images by Richard Koenig; taken June 12, 1976.