Boy JD that is a tuffy!...blastin or stripping and a good primer sealer is abought the only sure way, but for now if you could find a dry garage or barn to keep it out of the weather would surely help with at least some of rust from growing.
As far as rustoleum "NO" it will not convert it just cover it up for a while.
There are several manufacturers of rust converting coatings, Eastwood has a 2 part sysyem you mix 1 to 1 of each part and brush it on it worked fantastic on my cabs windshield frame, I then followed up with there rust encapsulator in that area.
To cover your truck in a rust converter would surely be EXPENSIVE!.
Tim
