PSA had a complete lpk w/ buffer tube and collapsible stock yesterday, but I don't see it today. IF you were able to find a stripped lower that's what I'd look at. If not, get a regular lpk and you can find buffer tubes and stocks out there.
The upper will probably come with rails, unless otherwise stated. If you buy a complete upper, make sure it comes with the complete BCG at a minimum, and preferably the charging handle also.