Wash you mouth out Doublin!!

The Holden Torana Club of SA inc has been around since 1991.
Speaking of shows and events, a few years back the A9X Club (of which I am also a member) held its Nationals in Adelaide. It was a three day event with decent goody bags, full judging, car display inside the Clipsal 500 event (including complementary pass to the event) Dinner and trophy presentation, tour of the Holden facility at Elizabeth, cruise through the hills to the National motor Museum at Birdwood with a relaxed BBQ lunch and tour through the museum. If there's enough interest, there's no reason why something similar can't be organised for an XU-1 event, either using Clipsal or Classic Adelaide as a basis.
Re the judging, a few general comments and suggestions, from crusty old bugger that's been judging and organising shows for way too long. I believe that one of the best judging systems around is one that was developed by the Street Machine Association of SA (SMASA) over a number of years, when it was running shows with up to 400 entrants. It had a classification system that was based on the following criteria.
Restored/Original - no attempt is made to distinguish between whether a vehicle is in an unrestored condition, or whether it has been restored. It is just too hard to draw the line as to whether a car is untouched, has minor work done, or has had a major authentic rebuild. The criteria for resto/original is that the car must be to all intents and purposes in original condition, or as close as you can get to it with currently available parts. No extra chrome, no stereos if not oem, no pink spark plug leads, no racing harnesses, electronic ignition or sports wheel, etc. The ONLY exceptions were safety related items, such as fitting seat belts if not oem, fitting of fire extinguisher, third brake light etc. It's not to concourse level though - radial tyres (as long as they are about the right size), aftermarket oil filters, spark plugs, etc are OK, once again, as long as they perform a similar duty and look similar to period items.
If a car had ANY mods, then it was assessed with a detailed classification sheet that allocated points (classification points, NOT judging points) to each modification. If the car was only lightly modified and the classification points added up to less than 40 (eg CD player and a small amount of engine bay chrome), then the vehicle was put into 'contemporary' class, which is a class for quite original vehicles, with minor mods which don't detract from the overall original look of the car.
If the classification points exceeded 40, which indicated that the car looked quite modified to the casual observer (eg aftermarket mags, stereo, steering wheel, retrimmed interior, chrome, etc), then the car is put into what is known as body style and year classes.
For extremely modified and/or detailed cars, including a detailed undercarriage, there is a separate 'show' class.
For vehicles with a proveable race/competition history, there is a competition class.
Once each car has been classified, the classification is explained to the owner, and written on a sticker on the car windscreen, so entrants and public can see who is competing against who. Every car, no matter what classification, is eligible for general trophies, like top overall, top engine bay, interior, exterior, etc, and there are also trophies for each classification.
If any entrant was unhappy with their classification or another entrant's classification, it was up to them to lodge an appeal, and if it was directed against the authenticity of another vehicle, or its right to be in a specific classification, then the onus was then put on the owner of that vehicle to prove its authenticity or eligibility for the classification.
Might sound complicated to read all at once, but believe me, it works pretty well, especially if explained up front to entrants. It was fine tuned in many many shows, judging thousands of vehicles.