I haven't fueled up yet but I thought I would share what I did with my tank vents. Many 6.9 trucks have a slow fill issue due to poor venting, also the truck will not take a semi truck style diesel nozzle with the stock filler neck intact.
I removed all of the "guts" from the inside of the filler neck, then I replaced my rollover valves with some nylon elbows that are actually pcv elbows. I routed the 19/32 fuel line vent to the plastic filler housing where it vents.
According to my primitive measuring, it will clear no problem (these elbows are only around a .25 inch taller than the stock rollover valves). Hopefully it will take fuel at a reasonable rate. Now I just have to make sure I don't roll it over!
That's how I did mine on my diesel, and it works very well. I didn't have those nice plastic elbows though. You may still get a little contact on the rear elbow to the bottom of the bed. It's very tight in that area.