[clutch-monkey]

the cars are all the same, just pick your engine and trim level, and you're done.
this article circa 2001 sums it up towards the end:

In understanding the Holden vehicle line, it helps to abandon your current notion of American platform engineering and branding; most of GM's US cars have totally different platforms, manufacturing plants, powertrains and styling, which means less economy of scale, subcontracting and shipping nightmares, lots of marketing tomfoolery, and extra cost passed on to you and me. The Aussies cut right to the meat of things: the cars are all the same, so pick your price/trim level and pick your engine (think Chevrolet circa 1957).

a little in detail:

Turns out the LS1 isn't the only performance powertrain. Just under the 225kW LS1 (called alternately the Generation III V8 or the Heritage V8 in Australia), is the Ecotec supercharged V6. Rated at 171 kW (that's 240 hp for us Yanks), the Ecotec supercharged V6 is none other than the Eaton-inflated 3.8-liter Buick V6 found in the Pontiac Grand Prix GTP and the Regal GS. The big difference is that it's driven by the proper wheels via a Hydramatic 4L60E. Even more exciting is that next year's Australian version of the blown V6 will be uprated to 200 kW (approximately 270 hp) and be available with a 5-speed tiptronic automatic trans.The combination of Holden cars and powertrains is staggering. It's like the old days when you checked off the order blank with whatever engine you wanted. You can get pretty much every car in the line-up with any engine, from the bottom of the line Executive VX, to the top of the line Caprice. Make sure you're sitting down for this next one--preferrably with a box of tissues: We priced out a Holden Executive VX (the entry-level four-door sedan) with the 312-hp LS1, automatic four-speed trans, air conditioning, power windows and door locks, dual airbags (they're optional in Australia), traction control, limited slip differential, FE2 performance suspension, standard IRS, and cop-sized 205/65R15 tires (for the sleeper look) and came up with a list price equivalent to $19,730 US dollars. Un-frigging-believable.

Why so cheap? Other than a trio of econo boxes, GM's entire vehicle line-up in Australia is based on this one platform--the Opel Omega-derived GM2800. Australia being a modest-sized market (only 19 million blokes total), GM correctly decided to limit the number of platforms to keep costs down. Costs are further reduced by importing all of its engines from the US--the number of those also being limited to just three across the entire Commodore line. (The entry level is the Ecotec V6, a renamed naturally-aspirated 3800 Buick, rated here at 200 hp.)

One last tidbit of heart-wrenching technical info. The powertrains for the LS1-powered Commodores are directly from the F-body parts bin, that is to say the engine and trans (both A4 and M6) are the same as Camaro and Firebird. There are only minor differences in calibration due to the reduced quality of Australian fuel.

Just Call It A Commodore

Like we said before, try not to get all confused by Holden nomenclature. If you really need help, there are web sites you can go to for enlightenment. We found the "Unofficial Commodore Archive" (www.uq.net.au~zznweber/commodore/index.html) to be extremely helpful in sorting out the names and dates. Also, Holden's official site (www.holden.com.au) gave us the low-down on the current VX range. ("Range" is an Australian term for "car line," but also makes additional inference to the year or years it was built.)

Here's a primer. Australians rarely refer to their Holdens by model year. They go by "range," also known as a "series." For instance, the LS1 made its first appearance in the Holden Commodore/Calais in 1998, which began the VT II series. The VT series (including VT I and VT II) ran from September 1997 to September 2000. We're now on the VX series (September 2000 to present). The next series will be the VY series. (Technically, the SS Ute is a VU series as it was designed just prior to the VX series, even though it was actually introduced to the public after the VX.) Series built previous to the VT offered Australian-specific powerplants (VP, 1991-1993; VR, 1993-1995; VS, 1995-1997), which is why until recently, Holdens rarely drew attention from American audiences. Now that GM is trying to share powertrains across its international divisions (i.e., LS1 Vortec and Buick V6), we now have reason to be curious--and envious, but we digress.

There is just one rearwheel drive platform at Holden, which is broken down into a short- and a long-wheelbase variant. The short wheelbase variant (at 2788mm) is the basis for the Executive Sedan, Acclaim Sedan, Commodore S, Commodore SS, Commodore Equipe Sedan, Berlina Sedan and Calais, while the long-wheelbase version (2939mm) is home to the Executive Wagon, Acclaim Wagon, Commodore Equipe Wagon, Berlina Wagon, Ute, S Ute, SS Ute, Statesman and top-of-the-line Caprice. Both short- and long-wheelbase RWD variants share the LS1 as either standard equipment or an available option. Every single one of them, we might add, features IRS and four-wheel disc brakes as standard equipment. Now imagine if you could get a 5.7-liter LS1 in everything from a Grand Prix SE to a Cadillac STS and you've pretty much got the picture.

obviously this info is out of date but it'l help you understand the naming method