BGT puts the BG1 content in the place of the BG2 tutorial, allowing you to play through the entire seriest in one continuous run, with the same rules throughout. Unfortunately, its a huge download and its getting hard to find. The part of it I've played is excellent, but there are a number of bugs which can be irritating. BGT forums are here:
http://www.teambg.net/forum/?s=deb73...7&showforum=94
There is also the similar BGtutu mod which is a much smaller, more intelligent way of doing the same thing.