1950 bed angle strips

[gab50]

I am trying to put new angle strips on my bed. On one side it was riveted in with a glassed over cover on the other side that you couldn't tell what was there. The other side has the original but has areas that are rusted through but it is still very stiff. The truck has very good paint on the outside so don't want to damage that. The areas where it was spot welded to the box side has been ground down so can't see them. Any ideas what I can do to get the angle strip off without damaging the paint on the other side. My plan was to bolt the new SS strips on with SS bolts. The new SS angle strips currently don't have any holes in them.