That was great advice. (It is one thing to ask for advice, another to take it.) By stripping all the primer I am able to distinguish the etching from actual rust. I am going to touch up the rust with the grinder. I have a picture of the truck from about the 70s I think and it has a roof rack on it. I am sure that is what caused the major rust lines. Thanks again Bill and Tim.

The wet sander
Bare metal 1
Bare metal 2