The US sold cars had to be made unleaded capable by 1974, The first domestic brand cars that had a catalytic converter were the '75 models made in '74. Many of the imports didn't have cats until later, deciding to try to meet emissions otherwise. Also, they probably weren't privy to the technology. Some of the German cars in the mid and late 70's had some thermal reactor exhaust manifolds that glowed in the dark. Some of the Asian brans didn't as well. 1980 Subaru's were the last man standing without a cat. Magazine articles described mashing the throttle on a 1980 Subaru as a barely noticeable on/off switch.
Half ton trucks didn't have cats until 1978 MY, three quarter ton about 1980 MY and one tons about 1983 or 1984 MY.