Learn something new everyday. I never knew that any aircraft other than the Lancaster had carried the Grand Slam.
Source. Link 1 & Link 2.
A news clip with photo, "Two 22,000-pound bombs were carried by B-29s toward the end of the war. British designed bombs were carried externally", shows a B-29 with two Grand Slam bombs mounted at hard points between the inner nacelles and the fuselage. View is from 4 o'clock low.Unless the pictured bombs are empty casings, this would be stressing the B-29 well beyond standard published limits. Most sources list maximum bomb load as 20,000 lb, while two Grand Slams would be 44,000 lb (plus mountings.) Listed empty weight is 68,800 lb, though this could be decreased by a couple of thousand pounds by eliminating the defensive guns and fire-control system; maximum weight (in some sources, overload weight) is listed at 135,000 lb. The plane in the photo appears to have a radome mounted between the bomb bay door positions. This probably reveals the presence of a RADAR system on the plane, either weather-monitoring or, possibly, targeting.