Ditch lights where already being phased out due to maintenance costs. I think the M-K GP40M-2 units were some of the first SP units to get beacons and ditch lights, but IIRC the failed SPSF merger was actually when SP started dropping the gyralight in favor of the ATSF style beacon. Some SP GE's (B23/30-7?) did get a solid state flashing system where a double headlight had the bulbs alternatly flashed, and one was aimed towards the left and the other towards the right (another Pyle product?).

The original proposed requirement for ditch lights did allow oscillating headlights as an alternative for an auxiliary headlight, but did not make it to the final rule (49CFR229.125). Since the FRA required "ditch lights" for anything over 20 mph, the railroads did not want to pay to maintain both ditch lights and gyra lights (except Metra).

I did see at least one each KCS, SP and DRGW unit that had both ditch lights and gyralights - there was no mistake it was something big coming at you.