The 87 15x7 lace wheels are not the same as the 88 15x7 lace wheels.
The location of the air valve is different.
On 88, the valve stem is between the points of the lace pattern.
On pre-87, it's at the point.
(on the bottom in this pic)
Functionally they are interchangeable. It's just that one minor cosmetic change. That may or may not matter to you.