I responded to your post in the Pro Cruiser thread. Check it out for more info.
In sum, it looks like you have an early mountain bike. Quite a nice save from the dump, too. In 1970s Marin County California, guys like Gary Fisher and Tom Ritchey would take pre war Schwinn frames (usually a straight bar DX -- looked like a Cooks cruiser) and make mountain bikes out of them. This was before any mountain bike was developed or sold commercially. The solid post is a common Klunker era modification because the mild steel posts would bend on the first ride. They resorted to solid aluminum because rod stock was readily available and strong seat posts in 13/16" were not.
What size seatpost did you use? The proper seat would usually be a Brooks -- a B72.
Do some web research and you'll learn a lot. Check out nostalgic.net for info regarding the Shelby. They might have catalog scans. Search the internet for klunker bike or clunker bike. Post some nice, bright pictures, too. You may have a real artifact. Very few from the era survived because the mild steel frames would become useless after about three months of use. Interestingly, the Marin guys spoke of a bicycle junkyard in Oregon where they would get frames, 80 at a time, to build into mountain bikes, something that would be unthinkable now. But, at the time, the old Schwinns weren't worth much.
If you have a period clunker, don't restore it, just clean it up. Most peolple don't know it, but you may have something pretty special that was part of a movement that significantly changed the last 30 years of bicycling.
Below is Gary Fisher's mid 1990s hommage to the Klunker.