Vee_Que;96745 wroteNot quite. They do start with a steel car, then cut the front and rear ends out enough to fit the transaxle, plus they adjust the wheelbase to the fixed length. So they did have to build new cars, not re panel volvos. Its a shame they didn't make then chev powered, its not like you can buy a 5l volvo v8 either....
Not anymore.
Since the beginning of the current 'COTF' model car (2013), the cars are very much a 'chassis car' - they do not have a road car centre section or 'turret'
The cages and basic chassis are control items, supplied by PACE innovations and they are all the same. Wheelbase is the same, as is the rear suspension cradle (supplied by Triple8), transaxle (supplied by Albins), brake packages, etc.
The engine must be mounted within a set of parameters and there is (as of the start of the 2015 season) a minimum engine weight.
The manufacturer specific items are body panels which are homologated per model of vehicle and parity tested (poorly).
There are lots of control items, right from brake packages to the pedal box (supplied by Triple8). There's still some areas for innovation - most common variations are the
front uprights, for which there are some specified parameters but some freedoms to work with/exploit and swaybar mounting and adjustment (though most kinda look the same now anyway).
Here's the fairly dummed down statment about what we're currently running, its a pretty old article but a good summary -
http://www.supercars.com/championship/rules-and-cars/next-gen-v8-supercars/
Your statement though,
@Vee_Que , is correct for the previous gen 'Project Blueprint' cars where the external dimensions had to fit inside an 'imaginary box' and cars still retained factory floorpans and a lot more actual genuine panel pressings. As the road cars grew up from VP commodore and EB Falcon, their racecar counterparts still had to fit in the box of external dimensions.
These cars were much more difficult to repair.
The modern Supercar is much more like a NASCAR than you may think.
Volvo engines must go back to Cyan/Polestar, GRM developed/formed panels and aero kits are Supercars IP.
Here's the spiel on the change to the 'Gen2' Formula, where multiple engine types are introduced -
http://www.supercars.com/news/championship/v8-supercars-blueprint-for-2017-and-beyond/
Read: where we go from the top 10 being separted by 0.3sec to the 'good old days' of Group A where the actual racing only involved a couple of cars and the gap between the front of the field and the rear, in terms of laptime, was enormous.
