When Fiat replaced the 600 in 1964, they upgraded the mechanicals, but kept the recipe. After all, it had been very successful for them. However, they did move the styling on from the tiny original; it became more car-like and a bit larger. Still quite cute looking though. Like the 600, a large range of body styles were available, you could even have a van or people-carrier. The versions that remain popular are the Coupe and Spyder, which were built in large numbers, but haven't survived too well. Both are styled to look very different to the base model, and very successfully! Later cars have bigger engines, and there were unusual specials like the 'Racer.'
The original saloon cars were fitted with a 550-12 crossply tyre on a 12-inch wheels, an alternative radial fitment would be a 145SR12. The later Special models had a 145R13 on a 13-inch wheel.
The Coupe and Spider started with a 520-13 crossply tyre as standard. This changed to a 155SR13 radial in 1968, with the option of a 175/70HR13 on a selection of option wheels.