First Grand Island trainer I've seen. And now, in actual vintage color (had to fix it a bit):
There's another full color overall shot of '462 included.
The photos don't show the airplane at Grand Island as it's flat as a board all around G.I. Grand Island became a B-29 Phase Training field and I'd guess this Fortress was part of the Base Unit used for building crew flight time when there weren't enough B-29s to go around.
I've got to head out right now, but I'll be back with some more research on this particular airplane....
Not airbrushed I don't think; I think it's either very faded yellow or possibly the type of film used? I've seen some other trainer photos where the serial is barely visible but the codes stand out well, and vice versa (OD/NG Yuma ships are an example). Also note the "GI" looks like it's painted over a previous code.
I think the original tail code was RC for Rapid City.
Back to my earlier post, I'd have to guess this airplane was used by the 6th Bomb Group on early Gypsy Task Force deployment. There weren't enough B-29s to go around and several crews flew B-17s on long over-water missions to the Caribbean. I've got most of the Base History from Grand Island in my "library" and it talked about the use of older Forts for all kinds of flight time building until B-29s became available.