Yes that's exactly what that line from the carb to the exhaust manifold does. It just tells the electric choke when it needs to be on or not when the motor is warmed up. Yes your truck will still work without it, but the electric choke will just run whenever it's already warmed up. Whenever I put a new manifold on the Jeep the old line didn't fit so I still need to find a new one, but its no big deal. As for your surface rust, just buy or borrow a DA sander and get after it, then primer time. I helped a buddy back in highschool with a bagged burban DA and primer before HeatWave two years ago, needless to say it took awhile.