look in the power distributio box under the hood, you will see an open fuse location for power seats. There are 10 ga wires that run from the box to the white plug on the firewall. What Iam getting at is your truck is already wired for the power seats up to there at least, you need to add the fuse and then you can use the power feed for your new seats.
You do NOT want to just tap into a 12v power wire, the seat motors use a large amp circuit, 30amps I believe. They need to get a good power source, the reason they are 10ga is because the seats use alot of power to move, tapping into another 12v sourrce will likely blow the circuit.
Ford wired up the truck for power seats even if it doesnt have them, to do it right you should use the existing power wires.

Been there done that!
My truck came with cloth seats, manual, but with air lumbar,so power was there waiting to be used, the problem was the air lumbar circuit did not supply enough voltage and the seats moved SLOW if at all....