SilverWook said:
Would the widescreen version have been anything other than a crop job though?
There is a murky glimpse of a widescreen used in a mixing session here:
http://www.widescreenmuseum.com/sound/fantasound1.htm
No, that's not the case.  Walt's original intention for Fantasia was both multi-channel sound AND widescreen.  How do I know this?  Walt Disney himself told me, on the 2000 Fantasia DVD second commentary track!  At about 61:41 minutes in, Walt says that he "planned to double the size of the screen", but that the bankers wouldn't let him, and he had to be content with Fantasound only.  I believe that photograph is proof of what Walt said.  What process would Walt have used?  Nobody's ever said, but I always suspected something like the 65mm process used for 1930's "The Bat Whispers", something that would have cost a lot more money to produce and is a 2.0:1 aspect ratio similar to the 2.14:1 dimensions shown in the photograph.
http://www.in70mm.com/news/2005/bat_whispers/index.htm
I forwarded this info to Marty Hart, but he hasn't ever updated his website.  I should send him another email...
Cserveguy