Not removing the lights every time I tow. Need a better option.
you can fight computational fluid dynamics, airflow science, and common sense all you want because " I don't wanna".
But at the end of the day, you are blocking "too much" airflow based on the scenario that you are placing the truck in.
Your choices are:
1. Remove the lights.
2. Buy a bigger radiator ( which might help your cooling efficiency enough, but I'm doubtful that radiator core/fin/tank technology will cancel out lack of airflow, as all of those radiator technological improvements still require airflow.)
3. Stop towing.
4. Try a cooler tstat. If waterflow increases earlier in the heat curve, this may offset heatsoak by enough to get you past the most heavy load conditions.
You may offset the time to heatsoak enough that your truck has enough "head room" to recover before overheating. Think of this as "scratch space" or "reserve overhead". your truck will "recover" going downhill when there is less load on the drivetrain. If your tow route is just one big gnarly, steady hill climb, this will not work out so great.
5. An alternative to the Tstat ( or perhaps used in conjunction with it) would be a high flow water pump. However a high flow waterpump will have diminishing returns without an effective means to cool the static water capacity ( you will need to do something with the radiator to cool water faster).
6. Add additional Fans that push or pull air through the IC/Radiator spots that have their airflow blocked by your lightbars. ( This may help slightly, but fans are less relevant the faster the truck is moving.
You might not like any of the options, but youre going to have to choose.
I've chased this sort of issue many times over the years when shoehorning V8 swaps into jeeps, yet still wanting to run big off-road lights and/or winches.