My 89 manual says 119 - 185psi. I have no idea why the service range would be different in any of the 89-94 models, since the top end is exactly the same....
There's nothing really specific to the 89 to watch out for. The only difference I can think of off-hand is the water pump oil seal. In 90 they added a second seal to help stop the leak from the water pump into the transmission area. If yours ever leaks, order both the seals from the 90+ to replace the single seal in the RH engine cover.
Good luck with it! I love my '89 :cool: