While checking out your heater hose fittings, I noticed the 09 and up water pump has provisions for the temp sensor. On the pre-09 models, its in the block. I'm sure this is due to the VVT changes to the block in those years.
@DionR do you know if the water pump pulley spacing is the same on the different years? Using a 09+ water pump on a pre 09 retrofit would solve the problem of needing the DIY thermostat extender for the gauge sender.