You can get away with a smaller van, something like a VW Transporter or Vito but as has been pointed out you won't have the headroom, which may or may not be important.
Main thing to check is that the van has tie down points mounted to the floor, so you can use rachet straps to anchor your pride and joy in place.
Also get a long plank, or two shorter ones and lay one on top of the other but extended to make the run into the van shallower (if you can understand that). If you have a paddock stand use that, but it isn't essential.
I personally use 2 straps and pull the bike down from around the subframe area downwards to the two central tie down points, and put a cable tie on the front brake, never had a problem yet.
You can do it on your own, but I'd recommend getting someone to give you a hand the first time, probably the hardest bit is getting it out of the van and down the ramp/plank until you're used to doing it.
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