Great photos, and a nice Mainstreeter, but I think you need at least one more unit in it! Even in 1970, after the BN merger, with most of the mail contracts gone, and the train down to 5 or 6 passenger cars and a piggyback flat or two, it always had two units when it came through Pasco. Usually an AB set, but rarely an AA. I can count 11 cars in your picture, so I'd suggest at least three units to look right.