Yes you can use the Jackson Racing SC with the stock motor, internals and clutch. But they will have to be done sometimes. Why not do it all at the same time and not have to worry about it, and have your car down for a few days every time you have to upgrade one of the components?
Remember the stock GSR eng. is rated at 170 bhp and you want to take it to 250bhp that is a dif. of 80bhp so you will have to run a little bit of boost than normal. Just ask yourself a questione, do you want to spend the time and do it right, or do you want to just slap on the SC and have to go through lots of headaches later on when something is going to brake and have to spend the money anyway, and might have to fix something else in the proces since you didn't do it right at first. Well all I can do is give my advice and I think that is what "sinfestboy" was looking for. "A safe 250 supercharged hp in a GS-R.... " So have fun and good luck. Stefan525