Originally Posted by Robert Harris
2.55 would work beautifully.
According to IMDB the ratio is 2.76:1 (wider than Cinerama.)
And 2.50:1 is "recommended." According to Widescreen Museum "The chariot race as seen in the full 2.76:1 70mm aspect ratio. Ben-Hur's spectacular photography was matched with its extremely vivid 6 channel stereophonic sound. For practical reasons, the film was shown with an aspect ratio of about 2.5:1 in most roadshow houses."
Still, the Blu-ray will probably be 2.76:1.