General rule of thumb is:
- Rere's are allowed.
- Vintage cars from that era/class are of course allowed with any mods available from that same period. i.e. an Optima Mid with alloy bellcrank steering, lwb conversion etc. Anything you would have seen for example in 1987/1988 for an Optima Mid is OK which makes sense.
- Wheels aren't police'd but I like to run correct wheels. 2.2 inch look silly and some cars are just too narrow for them without modern updates.
- Slipper clutches are allowed.
- However, for example, am Optima Mid with ZXR arms/towers and Cat K1 big bore shocks isn't cricket as these mods wouldn't have been available back then. They should compete against modern buggies which I'm sure is still fun for the driver/owner.
- Power systems/electrics are open - run brushed or brushless assuming your transmission will not give up - which is your risk
But yes it is hard to really control without spoiling the fun of vintage racing....and it is BIG fun
Cheers,
Dan