I am prett sure you can fit an Ecitech straight in however you will need to change the wiring loom and ECU to get the sequential inhection to work. I was told the motor can run on the older ECU and wiring with some mods to some wiring for sensors which are in a differnt place for example but the injectors will not fire sequentially anymore.
Don't want to be a downer on the topic but they give VS's away, unless your car has some huge mods that can't be transferred from your old car to your new one it would be financial suicide!
Just my opinion though.
The ecotec will fit in, although the VT's have an egr valve. If you are going to do the conversion you will need to either plug up the hole into the Plenum or change the Plenum to a VS one, very easy to do. Can pick one up from the wreckers. You will need the exhaust off a VS, you will also need the wiring loom and ecu from a VS. VT's use a different sensor from the Coolant temps. In all honestly it would be cheaper to go buy another VS or VR. You would also need a VS gearbox.