1983 300sd turbo w126 body

i have no rust... but i want to live to 100 and i am 42 so my car needs to last another 60 years... i was thinking about doing some rust prevention..

does anyone have any rust prevention ideas..

perhaps i could sand blast the undercarriage an then put new undercoat on.

or i could just put new undercoat on over the old...

why do you think