There is already an exhaustively researched game. The author actually got permission form Black Isle (Fallout 2) to use a good amount of the intellectual property - SPECIAL system, gun images & descriptions, the pipboy character, even the damage calculations right out of the game. (though that last one does complicate conflict a little) It come out to be a quite hefty and professional looking document. Despite its age, you probably should give it a review on the free rpg blog - though I am quite aware you have a sever backlog at the moment.
Go up a level in the , and there are a half dozen source books and some other contributions.
These were written years before Fallout 3 came out, but this isn't necessarily a problem. Many elements (too many in my opinion) are recycled in the latest edition - so you still have all of the equipment (with the classic descriptions rather than none at all) and creatures - several times more of each in fact. Furthermore, I take issue with how a number of items are represented in F-3 (power armor and super-mutants are two big complaints) while the the old PnP game still represents things as I (and many other fans of the series) believe they should be.
I recall seeing a game on either 1km1kt.net or RPGlab that used the newer version of SPECIAL, but I cant find it at the moment.
Anyway, a Fallout 3 source book might work, but there is already a good Fallout table top RPG on the net made with the blessing of some of the video game's producers.
On a related note.....I am dieing to get some people together to build an Arcanum pen and paper RPG.....it was made by the same lovely people who did fallout 1 & 2. steampunk with magic!
Time Fly's like an arrow! Fruit Fly's like a banana!
I found a few a few for the Unisystem (AFMBE/Witchcraft) a couple of years ago. Given the scope of the video game, I wouldn't call 19 pages nearly enough, but it should at least help you get a start. There is also a run-down of the territories and a map on that page.