Ray, I asked the same question when I installed mine, and Don Bock at AAW explained to me why they chose to lay it out that way. There was a technical reason that made it better, and I am sure I wrote it in my project notes, but it has been too many years. You could always call the AAW toll free and use the dial by name function to call Bock.
I wrapped the wire from the starter to the alternator in harness wrap, and included it with the wire bundle coming down the firewall to the starter; when the wire got to the bottom of the heater box cover, I ran it underneath the box using the same kind of clips used on top of the heater box cover to hold the orange heater fan wire. It runs under the heater box cover, out and over the top of the inner fender (in the hidden part; that length of wire I wrapped in the more modern convoluted tubing to protect it against abrasion against the fender bolts or rough edges, etc). I brought it in by the battery, where the wire from the front light harness comes in for the voltmeter or idiot light, and ran those two over to the alternator together, again wrapped in OE type harness wrap.
I can check and see if I took any photos, if my description is unclear. Donny told me to just run the wire to the alt alongside the oil pan rail in the clips with the battery cable, and then up the block to the alt. But I decided to do it the way I did because I am generally trying to keep the underhood stock looking, and I thought it would be weird to have a wire up to the back of the alt, where it is not normally, and I didn't think it would be as protected as I have it now. Yes it is a well insulated wire and supposedly is rated to handle that much heat and more, but I did not want it that close to the block, especially because it is a 12V constant hot. I wanted it protected...
