Inside of metal panel coating?

All the suggestions are good. You definitely what to get some type of paint on them whether it be primer or por 15. Besides that I would look into a chemical call cavity coater by KBS coatings. Other companies sell it to under different names. It is basically a spayable paraffin wax that creeps into any crevices . I use it on the insides of rockers, quarters, door frames and hood frames etc. Basically anywhere I am uncertain about full paint coverage. I am doing a full resto on 60 Dart Phoenix right now and have used it on any panels I replaced or stripped. I use about 5-6 aerosol can on each vehicle I do.

Cavity Coater

Thanks
James From
PST