I'd be afraid to try to crank my engine if it was killed by water. If it's flooded (with water) you could do all kinds of damage. It won't rust in the time it takes to remove the engine so you can flush it out with WD-40. Make sure there isn't ANY crud in it before you crank it back up. Who knows how many thousands of times a grain of dirt will make it's way around your engine while you try to evaporate the water!

Plug the exhaust & carb with rags & take it completely out of the truck. Then blast the outside of the engine with alcohol, nitro cleaner, or carb cleaner (my fav but make sure it doesn't have anything in it that will eat plastic or rubber like Acetone or Xylene. I use Advance Auto Parts Carb & Choke Cleaner). Next remove the rags, glo plug & head. Don't spare the cleaner when you flush the inside. Inspect it for scratches & a bent connecting rod then WD-40 the inside real good then reassemble making sure you don't get any dirt inside of it. I always put some after run oil in it after cleaning. Good luck!
If you're mechanically inclined, remove the pull start & backplate BEING SURE to take the starting pin & pressure spring out so you don't lose them. They are in the bottom of the connecting rod. Be sure to locktite your screws as you reassemble! Good luck!