Ignition timing

First, you have the 5.7L not the 4.3L if the distributor is on the front

Those distributors just bolt down , they don't have a timing adjustment... its all computer controlled. If you are having performance issues, scan the computer to see if any codes are stored.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing



See the diagram below for your distributor