It takes just a moment to join our fantastic communityRegister
You are most certainly correct there i posted before i looked at the back of the car and on further investigation i think sv8 tail lights are the smaller executive size as such a rear bumper swap will also be needed.If there is any difference, it's not that they don't bolt on. They will. Holden didn't make sheet metal different for Calais. The difference will be how far down they go. To which, a Calais bumper is required.
Calais has reflectors in the bar. light is slightly bigger so either cut your bar to suit the difference or buy a Calais bumperDo the Calais ones have the reflectors in them?
From memory thats why the Calais also had a different rear bumper to make it ADR compliant with the reflectors.
Having a quick look on Holmart they do indicate that the Calais/Berlina ones are bigger than the exec ones.