There are a few peculiar things about this frame. It's definitely Murray built which supplied Sears, Western Auto, Hiawatha, Mercury, etc and could have been badged any of these pretty much with no differences in the frame.
The peculiarities I see are that it has no tabs for a tank. I've never seen one of the chrome space bikes without the option for a tank. They could have been popped off over time but it doesn't appear so.
Second thing: this is a true cantilever frame, which I've never seen on the space bikes. It turns up on later frames from around '65+ but I've never seen a chrome bike with this frame. Look closely at how the seat stays go right past the seat tube and loop all the way to the downtube. Then look at the picture of the Flightliner frame. It's a faux cantilever since the two bars start right at the seat tube. This is because Schwinn had a patent on the true cantilever frame until 1959. 1959 was also the year the Flightliner came out, so they designed the frame as they were allowed to in accordance to the Schwinn patent.
I'm sorry that I only made more questions than answered them! I don't know of a chrome model that came tankless, and after the switch to a true cantilever frame.