Insurance is a good point. My first Mini was in 1969. Insurance was £60 because 'too many people of your age group are writing them off, or seriously injuring themselves in them'. It was a standard 850cc and would never achieve motorway speed limit.
I was paying £78 for my modded Transit from 1985 until 1990. When I started with the AA in 1987, I got a staff quote. First question was as to who modded it. When I said I had done it myself, I was quoted just under £800. I declined their offer and paid the £78 for another three years.
A friend of mine used to buy the same car as me whenever I changed cars. In conversation one day, I discovered he was paying more than twice as much as me because he didn't shop around.
I think insurance was not as aggressive in those days, when I told them about my modifications (by letter, letters were affordable then) they wrote back with some questions.
Had I increase engine capacity - No
Had I increased the number of carburettors - No only a single carb.
Had I altered the body - No
Had I altered the chassis or wheels or brakes - No.
They then said, the insurance would same as an 850 Mini, and would I please stop wasting their time or words to that effect!
Being ever so polite 'cause I was well brung up I didn't argue.😉
I had one claim while I had Minis, caused by an out of control E type coming the other way wiping me off the (wet) road, my insurance was comprehensive, and in those days they sent an engineer to asses the damage, the car was fixed, and someone payed but not me.