Can I ask how did you check to determine it vents both ways? I've had a hell of a time finding one that fits that vents both ways. Any chance you have a picture?? I'd rather have one of those.

And IDK about the return line as I do not have one. There was a guy on the google group list had an issue with his almost new pump that was NFG and returning most of his fuel back to the tank instead of the carb(y) when it got hot the car would die. I haven't had any vapor locking issues yet without a return line.