Vent and here is why.
In order for air to pass through the radiator, it must have somewhere to go. You cut a hole in the hood, or the fenderwells for that matter, to let the air
pressure out from the engine bay. The drop in the bay pressure will allow more air to pass over the radiator tubes.
Here is the kicker, the "where do I put the hole" kicker.
There are two basic places to cut. Near the froont of the hood and past center nearer to the back of the hood. If you wish to increase flow at higher speeds, you cut at the front, lower speeds, at the back.
You can test it yourself by taping 2" pieces of yarn onto the hood of your Heep and taking it for a drive. You will see the pressure areas and air flow develop on the hood by how the yarn reacts. In a low pressure area, it will stand up. You will be able to see exactly how the air moves across the hood by the pattern the yarn makes. Use a maximum 6" grid. When you find the lowest pressure area on the hood, that would be the best functional location for a vent. Get the best scavenge effect.
Here is where I mounted mine on the 98:
And here is where I put them on the 97 I had:
Scoops are for cold air intake...
Before anyone asks, the vents on the Black 97 are from a Nissan Z car. As you can see, I mounted them as far back as possible. When I did my current Red 98, I was investigating the engine cooling system. I was working with Davies-Craig (out of Australia) to get the EWP115 system installed and fully functional. Poking these vents (which total 72insq) made an immediate drop of 7F in the average engine temperature.
Which is a good drop.
So, there is my .02 on the subject!