Actually one of the main reasons we used this 60 to restore is it was 100% rust free. Basically the underside was scrubbed with purple power or the grease remover of your choice, pressure washed, scraped, scraped, scraped, then finally sanded down with a DA sander(mostly on the frame).
The underside was sprayed with undercoating available at any auto parts store. They have thick and thin styles. Frame, springs, axles, and other parts used rustoleum satin black.
Easy to do...just dirty and time consuming. A steam cleaner would work great.
More pictures to come. Should be on the road in 1 week!