1989 Chevy Astro serpentine belt

I will provide the detail needed to replace this from the manual. However, here is a guide that will help with this as well:

https://www.2carpros.com/articles/replace-serpentine-belt

Please see the diagrams below that will help with this replacement.

There are multiple options for the 4.3L so basically you need to match your pulley arrangement to the diagrams and then that will show the routing for that arrangement.

Please let us know what other questions you have. Thanks