9's come both ways. As pointed out, it could be the 350/400 and/or w/w/o ac. I don't know. I do know that you could get 350 cars converted to 400 cars by new car make ready. Whether or not they went to the point of adding return lines on such conversions is a good question.

I'm not positive but I think that CA emission packages required the return line, meaning that a 350 2/bbl car w/o ac may have a return line.