Louvers - Thought to be needed because "heat rises".
Well, no, to be technically accurate, heat does not rise.
Heated air expands, gets less dense, and the buoyancy relative to surrounding air pushes it upward - if left to itself.
But, this is a forced air cooling system and the air is never left to itself.
The fan is always running.
New air is always being pushed into the engine bay, so the old air has to go somewhere else.
New air is very turbulently mixing with the old air, as well.
Where's it gonna go? Down and back, of course, where there's a great big free opening.
Aside from active mixing (dilution), the force of the engine driven fan is far greater than the force of buoyancy, by, I don't know, orders of magnitude?
Careful observers have tested the louver idea, many times over, and found it to be - no benefit.
This isn't the first rodeo for turbocharged 80 series Landcruisers.
Stop your handwringing and worrywarting.