In overall dimensions there wasn't much between the DC-3 and the Lancaster, but power and weight were a little..... (rounded figures)
Lancaster (in late war use) Span 102', Length 69', MTOW 68,000lbs, Total power 6500hp
DC-3 Span 95', Length 64', MTOW 25,000lbs, Total power 2200hp
When the film was made in 1955 a lot of the bouncing bomb details were still classified secret.