I feel like a professional on this subject because I have fixed stalling problems on my truck on 4 seperate occasions.

The first time was the ignition harness that was mentioned earlier. When mine went out it would stall while driving and no dash lights would come on. I could work the key switch back and forth til the dash lights came on and it would start right up. New ignition harness and problem solved.

The second time was the infamous PMD/FSD. When mine went out it would stall while driving and sometimes start right back up, sometimes I would have to crank on it for a while. New PMD/FSD and problem solved.

The third time was the also infamous OPS. It would only stall shortly after restart when the truck had been driven and shut down for a short time period and would require some cranking to get it going again. New OPS and problem solved.

The fourth time was the in-line fuel lift pump that assists the injection pump. Symptoms were serious hiccups under acceleration and stalling after startup with lots of cranking to get it going again. My lift pump sounded like it was working fine (humming when the key was turned forward and when the truck was running) but all it was doing was making noise and not pumping any fuel. New fuel lift pump and problem solved.

I don't know how to explain it but I love the truck. My next truck will be a 6.5 also. I guess because I know the engine so well that I feel like I can diagnose and fix almost anything on it now. Good luck with your problem!