I have the Greddy kit on completely stock internals and my engine has 135k miles on it. If you have to worry about smog, get the Greddy kit. Otherwise, go for something with a larger turbo for better power and the lower compression pistons so you can run higher boost. You don't need a rebuild if you are running the Greddy kit unless you have poor compression/static leakdown numbers. Get those two tests done and that will help you determine whether you should rebuild first.