Bill,

I think you have moved ahead of Advance-Design years when describing series-size designations on "fender spears" (as used/displayed on TF trucks?).

On Advance-Design trucks, the series-size designations were usually shown on the side of the hood (at 1:13am eastern time, your slip is understandable). It should however be noted that specific series-size designations were not on the hood side-plates from 1947 through mid-1949 (when the hood side-plates just showed Thriftmaster for 3100-3800 and Loadmaster for larger than 3800).

But, everything in your clarifying post is correct and helpful (although I prefer the GM term "panel doors" to "barn doors", maybe because I think of many barn doors as being sliding doors).