Hey guys,
Thanks for all the replies.
He bought it from a Ford used car lot. The warranty was through a third party warranty company. He had to fight tooth and nail to get them to replace the 1st dead transmission, they kept telling him the transmission failure is due to abusive driving habits (of course, without any proof that he drove abusively).
He later told me it started making a "heinous" noise the same day the transmission failed. That detail was omitted at first.
He decided not to press the issue with Ford and traded it in for a new truck.
So, it sounds like even if installation error caused the problem, his mistake was to keep driving it when a "heinous" noise was present. That is likely what turned a duff flex plate, from whatever cause, into a catastrophe.
So the catastrophe was preventable if he had simply stopped driving and had it towed.
One way to really make things difficult on yourself is to compound others' mistakes and your own bad luck with willful ignorance of the obvious...