After driving normally for about 20 minutes, got a backfire through the exhaust and engine stopped. Seems to turn over ok but will not fire. Unhooked fuel line at carb and cranked, getting gas ok. Thinking maybe a bad ignition module?? It's a 4.3V6 with 5speed manual. Anyone have any ideas what else it could be??

 

Check for spark - if you don't have spark, then that's likely. I haven't heard of this behavior on V6 trucks though. Let me know what you find.

So pull the air cleaner and look at the injectors while cranking to see if they spray fuel. If they're spraying, check the spark with a spark tester.

 

Turned out to be a bad distributor. Replaced and retimed and it runs great