It's a nice trail bike engine that becomes pretty dodgy once you breath on it too hard. Which is the most polite way I can tell you we aren't going to get involved in building any "monster" DRZ400 engines. I can certainly recommend someone who will be willing to do it, but you'd better be willing to back a Brinks truck up to his door. ;)
Put a good pipe and an FCR carb on it , and enjoy the reliability. ;)