I'm not sure by any means,but, I think they ran the daylight scheme with their passenger trains.Those are the red & orange E-8's/PA-1's.Kato did make them,but the only place to get them would be from a collector or eBay.
Good luck
Mike
The SP used GP9s with steam generators for passenger service, which were later passed onto a commuter agency. Details about the paint schemes can be found here
Luckily for you, Anachron you can use the easier to paint Bloody nose sheme..I'm the one left looking for the E or PA unit in Daylight Scheme Maybe I could go for the GS4, only thing is I hear it's a poor runner and the price this side of the pond is huge for something thats not A1.
"The Lark" was the night time version of the "Daylight" and was generally used on the same routes. These trains would have more sleepers and head end cars (mail) than the Daylights. Photos of these cars in "Daylight" consists was not rare. To fill out the mail cars check www.wheelsoftime.com for kits to produce many SP specific cars.
Power depends on era and passenger steam, PA(all schemes), GP9(any scheme), SDP45(not available in Nscale without kitbashing) would all be appropriate