Slight Miss

I had an old Crane HI-6 box go out on me before. But that was after my car sat for 3 years. My box just wouldn't work all together, no misfiring or anything.

-When's the last time u changed your fuel filter?
-Why are your plugs gapped at .039? Stock is .054. If you have an after market ignition you can actually open up the gap to .060. But I'd at least run the stock gap for a 5.0.
-Are you running platinum plugs? I'm not a 100% sure why this has happened...but in the past I've seen numerous posts on people having intermittent sputtering problems after installing high dollar platinum plugs. If you do have platinum plugs...loose them. Regular Autolite or NGK plugs will do just fine.