Those old IHC trucks are indestructible, I know after trying very hard to wear out my old '70 short wheelbase HD 4x4. The only body problems were splits, the steel was so heavy it would develop stress cracks. Every year or so I'd take a drill and punch a hole at the end of the crack to stop it's growth. That truck had leaf springs front and rear, the ride was "rough" but with 4x4 and Dana power lock front and rear, it would go anywhere. I used to say it would climb a tree if the bark didn't tear off! Best truck I ever owned!!
Every fall I'd load 10w30 in a sprayer and spray the underside getting oil into every nook and cranny. Dripped for awhile, but didn't rust. LOL