Bought a 73 mavrick some years ago,made the mistake of removing the vinal top.
Looked like some one went down the roof with a meat clever.
It had holes and rust all the way through it.
I treated the metal about three times then sand it down.
I put duraglass on it and smoothed it out.
After that I gave it to a friend and he sat it under a tree for almost three years.
The rust never came back and the duraglass never poped out like you see on alot of cars.
Kurt