There was a story I've heard before about Whirlaway getting run down on the lead in the one mile Derby Trial as a 3/5 favorite a few days before the '41 Derby.
Supposedly, Ben Jones took a knife and cut away one of his blinkers in the paddock on Derby day - he won the race by 8 lengths in record time....and his win in the Preakness next out featured one of the most amazing last-to-first wins in a major stake - along with perhaps Damascus's '67 Travers.
I guess that qualifies as a blinker change if the stories are true.