The k20z motor from the Si's are a bit diff then your typical k20a's. first is the throttle, it's no longer a cable, it's through a sensor that determines how much throttle your giving at the pedal. second is the tranny, they also have the 3rd gear synchronizer issued along with all 6spd k20 tranny, also the LSD on the k20z's that were equipped from factory then to be weak.
Oh snap im sorry just seen your said the 05 Si, from the hatch?. k20a3?. 600 good buy the only difference is the head and i believe pistons. . but if your building id say go k24a4 from an '08+ accord $600-800. slap a type s head for around 600.
Try this. car-parts.com
Also the above info is very useful..
