You never know. I've seem cars with shot frames where they just basically build a new frame around what's left of the old one. Even if you can't count that as original, if you want to keep driving that old car around, that's an option if that's what needs to be done.
We can always make the "Corvega" from the Fallout (game) universe. All analogue instrumentation, no computers, a vacuum tube AM/FM radio and 0-60 in 0.5 seconds.
I know a fellow amateur radio operator, he still drives a 1964 Rambler American 990 he bought new in 1964. He said one time that he is "waiting to improve cars" before he buys a new one. I looked up his birthdate, he was born in 1914, 101 years old, still drives. He drives with one hand on the wheel and the other holding the microphone and he yaks in the radio and drives been doing that since the 1930's I'm sure.