Given the enlarged cheek windows, paddle-blade props and shorter pitot tubes - I gather this is a Vega-built B-17F with a B-17E nosecone retrofitted. Thanks for sharing!
Interesting that the bottom two airframes have an astrodome, but a B-17E framed canopy. 41-2473 is using an insignia that dates from May of 42 through June of 43. The bottom appears to have the bar added to the insigna suggesting a date after August of 43... Interersting photos.