Where is the no 1 post on 1989 Chevy 350 distributor?

That depends on whether the distributor has ever been removed and if the "mechanic" knew how to put it back to the original position.

Here's the simple way to find it:

* Ignition key OFF, put the keys in your pocket. * Remove the #1 spark plug. * Stick your finger in the spark plug hole enough to seal off the air. * Turn the engine by hand (using the free hand) until you start to feel compression against your finger. * Keep turning the engine until it starts to "suck" against your finger. * Back up until the engine is at the top of the compression stroke. * NOW look at the distributor rotor and see where it's pointing... That's the #1 post.