Look for a shop that specializes in dipping your body into a tank of solution that removes all the Rust,Paint and grime. The cab must be completly striped of all the inside and outside parts switches, gauges,door handles, window frames etc..
The cab will come out really clean to bare metal and will have all the Rust Body filler or visiual holes from where the rust used to be if there is any. Then you can coat it with a rust preventive material until you get to the body work if need be.
62Chevy in progress
You've never been lost until you've been lost at Mach3" Paul F Crichmore (Test Pilot)