Eric, I know you said the number is 17090, but is it possible that what you think is a 1 as the first number is actually a 0, that was an offset strike? The reason I ask, is everything on your bike points to 1953. The wico magneto the guy says he has would even be correct for 1953. I was speaking to another one of our members at Portland last week, and he is certain it is a 1953 model. Please take a good closeup picture of the clutch bracket from both sides and post it here. 1953 and 1954 used a bracket that changed in 1955.
Thanks,
Rick