If you insure a car for replacement value, the yes the insurance would be high. I never did insure for replacement on mine, and so it's a good thing it never got totaled.
I stopped driving the 64 probably about 1998. Interestingly enough, that kid I sold it to is now married and has kids of his own and moved to another state. With a twist of fate, my son who now owns my 2000 mustang moved to the same city and state. Last summer I visited my son and he suggested we go contact his friend and go for a drive in the old Mustang. Which we did. I got to once again drive it after all these years. Me in my old Mustang and my son in his relatively new Mustang, even though they are now both my old Mustangs.
My 57 was a "beater". It was a station wagon (not a Nomad) and had major rust holes in the back wheel wells. Every time I drove when it rained, the inside of the car would get very wet. As a 19-20 year old it was about all I could afford. Needless to say, no fuel injection. It had a major blow-by and once I stopped to get my daily quart of oil put in and the gas station attendant forgot to put the filler cap back on and it blew all the oil out and that was that for the engine. I used to call the car "Burner" . That was its name. These days gas station attendants no longer exist, and if they did, most would not know where to put oil.
Actually, I think there are two states that still have gas station attendants. I am visiting one as I type this. Oregon. No self service in Oregon, but they don't normally even lift the hood except maybe for the occasional little old lady.