We are in the process of deciding what windlass we will be purchasing. PSC recommended the Lofrans Tigres as the best fit for our boat. One of the considerations is whether we should purchase a windlass with the motor below deck or above deck. For our boat it makes the most sense to have the motor in the body, above deck, because we do not want to use up space in our relatively small anchor locker, that could otherwise be used for chain/rode.
We also considered whether to purchase a horizontal or vertical windlass. Again, horizontal is recommended for our boat because it is higher off the deck and therefore allows a better angle to the anchor.
Here are some links to windlass installation projects from the web. http://www.boat-project.com/mech/proj-14.htm