Rust inside frame rails

[Chatt69chgr]

I was looking at the rear frame rails on my charger.  Gas tank is out so I can see them pretty good.  There is some rust on the outside of them.  Surface rust.  There are factory cutouts in these and you can see through these holes to the insides.  Not real good but there is some visibility.  I see some surface rust in there.  What should be done about it.  Nothing?  Can it be treated some way.  Doesn't look like there is any good way to get a rust converter or protectant in there except maybe by spraying it.  I asked a friend and they said unless it was eaten through to for get it.  When people remove the trunk floor due to rust, I've seen where they painted the inside of these with POR15.  I don't see how you could use POR15 unless you just had to remove the trunk floor anyway.
Same question on front frame rails. 
So is the answer to just get all the rust off the outsides, treat that, and then spray a rust converter on the inside and then spray in some epoxy primer?

[green69rt]

I'm going to throw in my 2 cents on this. If you can't get to the inside of the frame rails then just do what you can and forget about it.  The metal is thick so if 40 years hasen't poked holes in it then a few more won't.  If you get the chance to take off the trunk floor, etc then go after the insides.  otherwise just spend a little time getting the crap out of the insides of the frame rails, then use one of the long tube sprayers (POR15 have one??) or a long handled cotton swab and move on.

[HOTROD]

Try this   
http://www.eastwood.com/
http://www.eastwood.com/internal-frame-coating-w-spray-nozzle.html