Hi Ethos,
The B-29 flight line and in flight pictures have the unique large and bold double digit numbers of the Alamogordo AAFld, a Second AF B-29 replacement crew training base. The C-46 and B-25 are probably transit aircraft at the same base.
The black belly B-29s look worn and has the straight propellers of a Pacific veteran, retuned for training duties. The others have the cuff propellers of typical of stateside B-29 units. Thus I would place the time frame for these pictures after V-E day.
Do you know if your grandfather was retaining on B-29s after his tour in Europe for deployment to the Pacific?
Too bad about the light leak on these photos, I would love to have seen a good photo of the flight line in photo 503-24.
All the best to you,
Tom Michel