I find that full conversions are sometimes too much of a hassle unless you're going to make some extreme changes. They are also kind of a pain in the ass to install sometimes.
Currently I'm working on a mod that will do just fine as a Custom Story, so I'm keeping it simple that way. It will focus more on story and atmosphere, and doesn't need any fancy hoohah. After this though I may be helping someone with a Full Conversion that will change key game mechanics such as health and sanity.
Also DamnNoHtml, I find that using black level fog does a really good job at creating total darkness, as it stifles most of the blue light. If the settings are tweaked in just the right way, it's nearly impossible to see in darkness, and the lantern light doesn't reach very far. My beta testers found it fairly imposing when I used it. >