I get the fantasy but this is silly. I drove a 1960's car as my first car in the 1990's.
There are dozens of things computers help with on cars.
Without a computer you'd have to let your car warm up in the morning instead of taking off immediately. You might even need to adjust the choke.
You would have to get a tune up every few thousand miles resetting and replacing ignition points, maybe replace or regap spark plugs, set fuel trim on carburetor, set idle etc.
Anti lock brakes are great also. Folks would be skidding all over the place.
Maybe a little less than some new cars but not zero. That would be a huge inconvenience.