Aw, too bad about that. I checked YouTube's Disneytv4me https://www.youtube.com/user/Disneytv4me and most of his Disneyland programs (although some look like B&W spliced-on openings & closings with color content -- from Wonderful World Of Color re-issues?) run 50+ minutes.

A check of the Fantasia DVD shows The Pastoral Symphony sequence runs 22 minutes and the middle centaurs section (Second Movement?) runs 9 minutes. If those school-educational versions have that middle part (or at least the pre-censored Sunflower segments) that might be good enough.

additional thought:
There is supposed to be a videotape-transfer-to-DVD of this Disney TV rebroadcast (still pre-censored) from the 1990's(?) floating around. That one should be the full 50+ minute show. Anyone know anything about it and it's content (I'm thinking the full Pastoral)?