Ok amigo, here's the wiring trail for both wires. Click for bigger pics.
The brown heater wire runs from the switch there on the outside of the wire highway (taped up wires) to the dash, then down to the fuse box like someone else said.
It ends up at the box and plugs into the side of the heater fuse thingy with a black or brown plug. Mine is here on the wrong plug, yours should be one lower than this.
Ok, now the sending unit wire. You already know it ends on the sending unit by the top water hose off of the radiator. You can get those at NAPA for a couple of dollars.
It starts behind the dash in the wire plug.
This is a weird pic, but it's looking up between the radio and the dash cluster.
Then it runs over behind the heater, hiding like a little girl.
I shoved my phone up there and got a pic anyway. Take that Engineering department!
It comes out of the firewall heahh, behind the coil.
Then meanders down past the starter heahhh
Then comes out Neahhhh with the alternator wiring (or gen if you have one). It's still dark green. And that's it. From here it just runs to the sending unit and plugs in. Tada!
*disclaimer: Please don't blow yourself or your truck up by following my advice. It's probably all wrong anyway.
