I wish there was a way to treat the inside of the frame rails. I blew them out and sprayed rust converter, best I could do.
QUOTE]
Eastwood sells a product for treating frame rails, rockers, etc. It is an aerosol with a hose and a special spray head on the end. You snake it through an access hole and pull it back out while spraying. No personal experience but I'm going to buy 2-3 cans this week.
I actually came up with a similar thing 20 years ago but never pursued it.
My 68 cuda is native NoCal and has more rust than I expected, but I'm not complaining!