OK, so that opens up your choices then. There are a couple of options if you want to stay garrett. You can do a T4/T3 hybrid using either the 50 or 57 trim compressor. Many people run those. Another option that is becoming more popular is the Holset HX30 from a Dodge diesel pickup. They are HUGE, but many people say the spool as fast or faster than a T4/T3 and are much better at higher boost levels. The holset also bolts to a T3 turbine flange so it will work with your stock exhaust manifold.