'88: "Checkerboard" center cap with black outlining the letters and grid
'89: "Checkerboard" center cap with no black outlining
'90: "Bowtie" center cap
Why on earth GM would discontinue only the '89 part number is beyond me. And yes, I do own a set of all three. My factory '89s, a set of new '90s that I used for about a year (for sale BTW
) and a set of new, in the box, never to be driven on '88s.