[TWOOD]

Wetdog,
I did exactly what you are inquiring about. I routed the wires from the dash through a hole in the transmission tunnel in front of the heater discharge. I used high temperature convoluted sleeving (blue stripe @300°) and attached it to the brake and fuel lines with cable ties. Lots of cable ties. The harness is exposed to a drive shaft/universal failure (like DV suggested) in an area of about 6" to 8" (from the end of the trans. to the protection of the steel frame that supports the parking brake. I intend to protect it, in this exposed area, with a SS plate mouinted to the inside of the frame.
When all of the wires from the dash board exit through the fiberglass firewall, above and to the driver side of the trans., the wires split into three groups. One routes to the battery, starter, alternator area. The second routes to the front of the engine via the left inside frame (under the engine mount). The third, obviously, routes to the rear of the car, as described.
I, also, did not care for the route recommended by the manual.
Hope this might help you decide.
I could email you photos. I really need to figure out how to imbed a photo in with this text.