a 650 will work perfect. for all the info on blow thru or any other turbo stuff you could ever want to know check out theturboforums.com look up a guy named blownshovel I bought my carb from him for an awesome price and it works great. If you really want to do it your self check some of the stickies in the carb and diy sections.
c&s and csu are both awesome carb companies well known for their blow thru carbs. I have also heard lots of good about pro systems.