my first questions are always: what kind of cars have you driven before?
and are you sure you need more power?
if you are new to 240s dont worry about the 400 and 500hp SRs, buy it swap it and learn to drive it, more power comes later....any year SR is capable of making good power...Id say get a later year for the mileage not the power potential...cause like someone else said at the price of an s15 swap you should just go rb or even 2jz
