I think I am having a similar problem... Turns over fine but won't hit a lick. Like you I switched the fuel pump relay with another and no luck. I also checked the inertial switch in the passenger side floor board. I'm pretty sure I can hear my fuel pump prime if I get somebody else to turn the key on while I listen in the engine compartment. Does anybody else have any other ideas of what the problem might be?

The truck was running fine, I turned it off for about 10 minutes and then when I went to restart it, it acted like it halfway started (ran rough for about 5 seconds and then died). Now it doesn't seem to be hitting at all. Like I said, good strong battery and turns over fine. Any ideas?

I have the 3.0L V6 manual transmission like the original poster.