You'd have no heating, that's your main difference. Unless you fit a separate blower somehow.
Those outlets go via your cardboard tubes to the heat exchangers, to the van- take 'em off and you've got no blow. But, some people have eberspacher/propex etc and so still have heat... Some people just value engine bay looks over toastiness.
The second issue is that those fan housings have been designed to be manufactured as cheaply as possible. They don't have an OEM bearing down on them, at least not any more, so they can do what they like to save cost without fear. In this example, it means that 50% approximately of the directional vanes that deliver cooling air to your cylinder heads and oil cooler have been axed- they're not there.
There's a general concensus of some pretty bright folk that will say that causes your cylinders to warp and your engine to run hot. There are also some people who disagree who have overheating or broken engines, and then you've got the folk who run this stuff and get away with it.
My lady's nan was 99 and still cycled to the shops every day- that wasn't because of her age, it was despite it.
Personally, I'd recommend sticking with the stock fan housing. Honestly, the only thing that I'd recommend deviating from stock with are carbs- if you can go twin, do it. Everything else, stay stock. I'd rather get to where I'm going than look good on the back of an AA truck.