[e rock]

For a 5-lug, it's measured from one hole to one of the two opposite holes. Technically, it's center-to-center, but edge to edge is easier to measure rather than eye-balling the middle of a hole - just make sure you're measuring on the same side of the hole.

If it's close to 5x5.5, it probably is. The only other popular pattern I can think of that's close is the old Chevy 5x5. Then it goes down to 5x4.75, 5x4.5, etc.