I believe that year van has an 5x5.5 inch bolt pattern (but don't quote me on that).
The best way to find out is to take a tape measure and "ball park" the measurement between two opposing lug nuts.
FMJ's use an 5x4.5 inch bolt pattern (or 5-114.3 mm).
Another dimension to factor in is the hub diameter and offset (wheel mounting surface to center of wheel or wheel mounting surface to inner edge of wheel).
BudW