I have those wheels on a '99 Suburban.
100% sure they are 5x5.
My van is 5x5 as well... also 100% sure.

Make sure you're measuring center of one hole to the back of the second hole (making sure to skip a hole) since it's an odd number of bolt holes.
You measure center to center when you're measuring straight across on even numbered bolt holes.
Could that be what's causing the confusion?


[Linked Image from farm3.staticflickr.com]