I’m a dent side guy but still appreciate a good bump side. I remember going with my dad to the dealership to buy his 1970 F250 then helping him deliver bags of feed in it. Straight up work truck.
Great question. It's usually on the passenger side top frame rail inside the wheel well area. They can be tricky to locate, but a good wire brush and some brake cleaner might help.
I hope you sold her to a guy in Texas. Where she be a home on a ranch or farm. Very little rust on her. Who ever owned before took really good care of her.