Screw, you would do either the Rippetoe 3x5, or the Madcow 5x5 Single Factor version.
I just gifted you a FREE 7 day Platinum Membership.
Use the Advanced Search feature to search for username: Sculelos. Sculelos is a skinny ecto like you who started with the 3x5 for a year, and then went to the 5x5. He put on about 40 lbs. in a year doing that. He also eats like a horse (about 7000 cals/day)...gotta do that part too! Anyway, skim through his journals and that might help you decide whether to start with the 3x5 or 5x5.
Lastly, USE that FREE 7 day Platinum membership as much as you can over the next week!!! You can do advanced searches for specific words, usernames, etc. You can look at members' picture galleries, get a larger avatar, and many other things you can't do with a free membership. A platinum membership is worth it in my opinion, and it's pretty cheap. You may decide you want to stay a platinum member.