So, exactly which race cars are deemed 'Hotrods'?

[nzeder]

I have always felt that the simplest way of checking a historic cars elegebility is to ask the question, Could this have been built in its day, meaning that the parts must have been available to the public at the time the car is depicting. This would stop later components being fitted, with the onus on the driver to prove whatever parts thay have fitted were available. Certain upgrades should be allowed such as suspension bushes, shockies, period disc brakes if they were available, better engine internals within the original type block, head etc, but basically if the parts were not available in the period, then they cannot be fitted

And that is what the T&C rules state as the "Objective"

see here

Objectives: This schedule is designed to provide a set of regulations for the use of period production based Sports, Grand Touring, and Saloon Cars in sporting competition while maintaining the philosophy of the Historic & Classic movement.

Where appropriate, the regulations have been formulated to preserve period specifications by preventing the application of technology that was unavailable for the period depicted.