Ironically Dave, it was only a few years ago that I proposed to run my car only at track days for the very reasons you state. The dated seat belt issue particularly, then the need for an MSNZ card (annual fee to be paid to MSNZ of course) if you had any rollover protection that intruded into the passenger compartment, or had full harness belts, was enough to put off anyone with a classic car in original condition who wanted to fit decent belts and a rudimentary roll protection without wrecking the originality of the car.

Taking the car off the road and buying a trailer and the attendant problems that entails, was the preferred and cheaper solution, than paying a rego fee for a car used for just 200 road Kms a year, (plus conforming to the farcical authority card system).

If you run a classic standard/slow/road car, you are not going to be working on it weekends, trying to extract a couple more HP as the car is NOT a race car. Your performance is relatively fixed, so you are on the track for one reason only. To drive it safely at a speed that would be considered illegal on the public road. Whether that is in a Classic Trial or a race series is merely a matter of choice unless you are too fast for the trials, which sensibly, have a (lap) speed limit.