What type headlight do you have in your van? Is it one of the plastic housing headlight units? Or do you have the 200mm rectangle glass ones?
+1 on madscience's comment. Headlights are designed to work as a 3 piece unit. If you only replace the bulb with a hid bulb the reflector and the lens will not put the light where you need it. If you do decide to go that way stay out of the kelvin range that emits a blue light. Your eyes will thank you for it. They may look brighter but your eyes are designed to see things better in the lower white to yellow spectrum. If you do go blue watch out for truck drivers with anger issues they may be tempted to huck golf balls out in front of you.
Did I mention that little cars with blue light spraying all over the place and fart can mufflers tend to put the angry sleep deprived night driver behind the wheel of my work truck.