GM Holden has announced today that the first Pontiac G8 engineering prototypes have been completed at the carmaker’s production site in the Australian state of Victoria, where they’ll undergo testing ahead of the G8’s US market debut early next year.

The first production versions of the G8 are due to roll off the line at the Holden plant in late 2007, with an estimated 620 cars to be completed each day. Along with the US, the Holden built sedans will also be sold in the Middle East, South Africa and parts of Asia. The export program will expand the model range at Holden’s Elizabeth plant to 18 domestic and 15 export vehicle lines.

The new G8 is the first North American model based on GM’s new Zeta RWD architecture, which was developed by a global team of engineers in Australia and will eventually spawn a range of new GM cars.