1966 was when the currency started to go metric. Nothing else was changed for quite a while after that. (1974 could well be right.)
I'm old enough to have completed my engineering course in imperial measurements, and with a slide rule.
I like the fact that I could visualise, say, what a pound of butter looked like. And I could visualise a square that was one inch on each side. So I could equally easily visualise a pressure of one pound per square inch; or a hundred pounds; or 5000 lbs (which was the strength of a very good high-strength concrete). Pressure in psi is still what you use to put air in your car tyres. I suppose one could learn to visualise a kilogram of butter and a square that was a metre on each side, and hence a pressure of so many kilograms a square metre. But who uses that measurement? Absolutely no-one, because they give it some fancy french name like a hectopascal or something -- meaningless.
And the days when you put a gallon of petrol in your tank and the gallon allowed the car to go so many miles. Easy to see and understand, and gave small enough figures to remember and compare. If, on going metric, they'd changed it to km/litre I could have got used to it. But no, that would have been too simple. They used the reciprocal of that, and then discovered that it gave them such a small number they found it was meaningless, so they multiplied it by a hundred. And now we're supposed to measure fuel consumption in litres per a hundred kilometres. What a crazy, ass-backwards thing to do.
So referring back to the TV screen, why not a 36" = 3' = 1 yard screen? Would you rather have a 914.4 millimetre one?