Atlas engine are packed really tight. I have upgraded several Diesels to PS-2 3V. The lighting LEDs usually involved some separate boards that fed off the R2LC HL and RL feature, with added diodes and such. Plus the typical Track power fed stuff.
I have a few TAS SAW Ver 2.0 boards from Atlas SD models. Probably has all the wiring and stuff too. Maybe even the light boards. My e-mail is in my profile if your interested. G