My brother wanted a stealth install, so the factory locations were used. For resale, he also wanted no permanent modifications to be made.
Here's a comparison between the stock 3-way offering from Harmon/Kardon and the new a/d/s/ components:

Here's the new tweeter mounted high in the door. A 1/8" thick MDF baffle was cut to mount the tweet and seal off the hole left by the stock mid.
Here's the a/d/s/ mid mounted to the door panel. Again, a custom baffle from mdf was made to get a perfect fit.
The rear fill sets required the same baffles as the fronts. They dropped into the stock locations and are covered by the stock grilles.