If you can pull over into a gas station and get your hands on some ice or a hose - that may be a better choice.......but if you boil over on the road it is best to shut the engine down. It will hot soak a bit, but the engine can't produce heat if it is not running. Some engines can get hot enough to lock up and then start right back up after they cool down (2.5 iron duke from GM is a good example) but the 4.0 is a completely different beast and is nowhere near robust enough to handle much more than 260f deg. Trust me, if it boils over - shut it down.

 

Do you mean stock pump or stock pump and stock injectors? brenspeeds hellion kit comes with upgrades for both.