Hi Jim- Goodyear Eagles were (I believe) still the standard for '89 with US 911s. Here's a shot from the Motor Week review of 1988. That certainly looks like an Eagle tread pattern...
and the delightful Video...
https://www.youtube.com/watch?v=lYqvXEbnjDY&t=287s
As a further FYI, Goodyear was the tire chosen for the 1988 Porsche-Indianapolis 500 Race Car, and Goodyear was also the standard for the 1984 US 911s (per Road & Track)
Hope this helps!