I have one of these also. At first glance they look to be newer than the straight bar CWC Hiawathas w/ the Indian head badge. On the contrary they're older by several years (about 1940, Shelby built) and use the less attractive badge w/ the train on it.
I don't know what the Hiawatha model was called. Shelby used the name "Flying Cloud" on a few frame designs from the era, this was one of them. I haven't come across a Gambles catalog of the late 30's/early 40's to actually see this bike complete and original. I have seen several complete and original Shelbys in this design but have yet to come across a Hiawatha like yours in nice original shape, mine's practically a rat rod.
Caveat, again, I've been wrong a lot lately. Hell, it's probably CWC built like everything else.
I am the purchaser of that hiawatha. I think those shockease forks are great. That is my third one. Maybe someone can tell me if I can call that one a "super Chief" or not. I am not sure what you could call your bike. I have seen some people refer to the correct tank for those frames as "cadillac" tanks, but I am not convinced this is correct. I have pics in my gallery of the other two. They are rear facing dropouts and I am uncertain of the years. My guess is 41 or 48 on both. The black and red one is original parts except the bars and taillight, in my opinion.