With the truck in neutral or park, get a large jumper cable and hook one end to point #6, and touch the other end to point #1. If it will not turn over, I would think the starter has a problem. Make sure both #1 and #2 are clean first though.

Also if this is the exact problem you had before and is the reason you replaced the starter, I would suspect something else and not the starter. If this is a new and different problem, I would lean toward the starter.