Been doing research for this bike. It is a project for a customer of mine. I am the mechanic at the lbs. The guy at nbhaa was able to tell me it was made in 1945 to be sold in 46. I don't believe it came with a tank but who knows. Would like to know what the fenders looked like and the fork if it was a springer or stabilized with any thing extra.
Searching the forum will bring up a lot of pics. I don't believe their fenders were particularly distinct, though there were deluxe models, with braces that stick way out. I have a Shelby Flyer that may be a couple years newer than yours. My chain guard doesn't look original. They had a fork called the "Shock Ease", which had the spring inside the head tube! Later, they produced a more conventional springer. Consider yourself lucky you caught the infamous NBHAA owner on a good day!
i have a 41 shelby built hiawatha that has the same frame as yours,has a tank that goes back to the seat tube,tank is longer than the safty cycle,has 3 gills on the front edge,no horn[i think gambles hardware got it a little less with no horn],top of rear fender bolts to the rear carrier so there is no center render brace,has the hiawatha train badge,wheels look like they are triple steps but im never sure on those,has the big wide chain guard like a aero but is flat no[no gruves?]got it from the og owner who bought it new in 41 to do his paper route,had aero in small letters on the top front of tank,cant think of the name but it had a vertical spring seat like the ones on an areo with the horizontal springs,cant get 2 it to post pics as its buried with a bunch of others,does not have the nultigroved shelby chain ring,i watched over the years,havent seen the exact bike,i think the stig or vince have one thats very similar