I seriously doubt you would be able to get anything - if you consider how even the same model of a car can change from year-year. Anyway, I suspect what the manufacturers use is little more than a generic CAD package.
If you posess a detailed anatomical knowledge of your car, I suppose you could build your own CAD model but thats quite an effort.
I would suggest using as much of the existing wiring as possible and not deviating from the current placements. Conceivably, It would be pretty easy to overlook something and run a wire past a hot part of the engine or exhaust, or even worse, have a fault in your wiring which generates a load of heat near fuel or hydraulic lines.
The best advice I would say is get a garage to do it for you or at least have your work checked by a mechanic.