I currently have 30 original paint shelbys in all different years and models. Mens and womens, from 1936-1951. I have over 2k photos saved of all different shelbys. Every time a Shelby pops up anywhere, I save the photos and details. As far as the big tank differences... only some of the facts here hold true from what I have studied. As per all bicycle manufacturers, anything option wise can be sold. Just like a car from the days of these great bikes. It has been disputed many times about Chrome big airflow guards being an aftermarket item and not offered from Shelby, not true. The fluted fenders have two variances, both made by wald. I have each variance, the lindell seats and seat posts.... dont get me started on all the differences. Even the airflow and arrow frames are totally different, not just in the down tube but also the steer tube and the two top tube distances. The curved braces fenders changed in 1941. Sure they look the same.... but they're not. Trust me. So as I stated, just because it's in a catalog, doesn't hold true. A drawing doesn't depict reality. Like the non existing concept airflow that people swear exists.... it was an artist's rendition of an airflow. I'll stop now before any more brains spew smoke....