The cabs should be basically the same. Sometimes when you cross the year ranges you will find differences for the mounting points on the interior as well as electrical connections. some minor some more work than it is worth.
For sheet metal, usually 99-02 , 03-07 classic
For the electrical try and stay 99-00 then 01-02 , 03-04 , 05-07 classic. There are some things from say an 03 that will work in say an 06.
It's not that hard to strip it all the way down to the bare shell.
Is single, extended, or crew cab? When you say Shot, are you talking body damage or rust/rot issues?