What a great project! I hope you can pull it off. I, too have been looking for interior photos of the Coast Starlight from the 1970s, to no avail. I imagine they're out there stuffed among shoeboxes and "magnetic" photo albums in various attics across the country. I doubt many of their owners read rail message boards, though.
I might be able to help you with some reminiscences, though. I rode the Coast Starlight several times a year between 1974 and 1978. I was a teenager living in Salem, and I attended a boarding school just north of San Francisco. I would use either the Oakland or Davis stations. I have fond memories of playing cards in the lounge cars, and of sitting in domes in the dark, or having breakfast at the counter in the "snack car." I had encounters with indifferent and surly employees, as well as some who provided excellent service.
I've been working on and off on some stories from those days which I will eventually post on my website. In the meantime, feel free to e-mail me and pick my brain. I'll try to remember what I can.
------------------
Trust God, love your neighbor, and never mistake opinion for truth.
-Mr. Toy
The Del Monte Club Car