Bullshark, I have '00 'bird engine, which should be very similar to yours (slightly different emissions equipment is all I know in relevance to this post) the engine wiring harness is separate from the underhood harness. They connect with 3 main connectors on the passenger side wheel well. They are named C100,C101 and C105. Here's a shot of what they look like:
I believe there is a 4th connector that is smaller and is used in the starting circuit (purple wire).
The computer is behind the passenger side strut tower. The engine harness (and subsequently the ecu) gets all of its power through those 3 connectors.
Some of the engine harness does go under the dash. These are called connectors 220 and 230. I'm not sure where they plug in and don't have a shot of them, sorry.
As far as the underhood wiring harness goes (for everything else including the relay/fuse box, fan power and relays, headlights, signals, headlight motors, etc), that is one big snake. I have mine out of my donor car, but it also goes under the dash (where mine was cut) and, I believe, goes to the BCM. I'm not too sure on that. I'm not sure of your plans, but I really don't plan on using this except I may cut off the connectors C100,C101 and C105 so I have both sides for my engine harness wiring, or just sell it whole. This harness is not crucial for the operation of the engine as long as you hook up your own fuse/relay box and wiring for the fans.
Here is a shot of my underhood harness:
The WHITE circles are the headlights
The big RED circle is around the connectors that I disconnected from the engine harness (that purple wire is in there)
The YELLOW circle is specifically around C100, C101 and C105.
If you look over to the right, you can see a blue connector. I believe that is either 220 or 230, but I'm not sure.
I don't know your intentions for the engine to give anymore advice, but this section and FAQ of
ls1tech has some great info.
I hope this helps and good luck:beer: