Even in fantasy land where Tundra/Sequoia motors are commonly swapped into 200s, it's still going to be a well into 5 figure job. The Tundra/Sequoia 5.7s aren't -that- much cheaper. And additional labor that would be required to "make it work in a 200" hasn't been documented or quantified, and of course would eat into the difference in motor price.
Regardless, you would be a fool to pay that kind of money for a used engine from a junkyard, and the labor for the mechanic to "figure it out", without any warranty whatsoever.
Regardless, you would be a fool to pay that kind of money for a used engine from a junkyard, and the labor for the mechanic to "figure it out", without any warranty whatsoever.