In the USA, the 1988 HAD seatbelt holders. ('86.5 and '87 did not)
The mirrors of the '86.5, '87, 88 were 'molded' more to the body...'89 they went to a mirror that had more of an aerodynamic 'hole' in it. (sorry, no pic)
The easiest way to spot and 87 Vs. an '88 was the '87 had a rectangle/square spoiler brake light (no pic) the '88 went to a more angled brake light.
(Only the Turbo's through 1988 came stock with spoiler)
Pictures here are my stock and original body (except wheels) 1988 Turbo. I am the original owner. Purchased in November 1987.