Fordlover-
Nothing wrong with new or used replacement motors. I put a used one with 55k miles on it from a wrecked Mountaineer in my 2006 Explorer that had 200k on the original motor. It was a Saturday job with a friend. Motor runs like a champ a year later. It turned out that the old motor was good, so I still have it in my garage, the torque converter was bad but 2 shops diagnosed it as a bad motor .....
So I pulled the motor again to change the TQ. Luckily, with the gas motors, the price was "change" compered to the diesels, $1600 for a complete motor with intake.
So yeah, while it's nice to have original stuff in the car, replacements work :)