The Caprice is the long wheel base version of the commodore (your G8?)
http://www.holden.com.au/vehicles/Caprice
its aimed at the luxury market im not exactly sure why you would use it over the normal G8 (who cares how much extra leg room the bad guys get)
I think the closest ford have to the crown vic would be the aussie falcon. maybe they should look at a LHD version of that.
Would be very easy to make a tougher police car version of it.
they already make them for australian police with basic upgrades such as suspension, dash and seats more...