Yeah, like I was saying the only place 'everything' plugs in is on the passenger side door sill. (no existing wiring under the console)
If you're going to try and build your own harness, you'll want to take a look at the Factory Service Manual for a wiring schematic. I can't read wiring to save my life so all I can offer you is... good luck. There are a lot of wires under there, more than you'd think since they condense down to just two.
Tell the junkyard that the seats and switches are worthless without the wiring harness and I'm sure they make an effort to go pull it for you or even better yet, pull it from the Jeep yourself.