Drew - not sure how you get a driveshaft in an oil pan, but it sounds more exciting than a little piece of metal.
I bought the 3.5 because I was getting less than 6 inches of vacuum initially and figured the powervalve was probably open at idle - certainly at that time I could screw the mixture screws in until they were fully closed and it didn't make a difference so I assumed I was pulling fuel from somewhere.
*oil pump driveshaft
Paul - Holley's recommendation is 1/2 of idle vacuum, but to be honest that only works well in a narrow range of vehicles that pull between 10-15 inches of vacuum. When it pulls a lot of vacuum or not much, the recommendation is generally wrong.
If you drove that truck with a vacuum gauge, you'd likely find that it has a lot more than 6 inches during cruise, and doesn't drop below 3.5 unless you really were hammering it, which means it's closed and not adding fuel
Also, need to clarify the "fuel at idle" comment. A properly working PV cannot, will not, is unable to provide fuel at idle, even if wide open.
Think of the PV as a spring loaded extra main jet, not as a valve that dumps fuel into the engine. The way it works is, when your throttle plates are open, air rushes by the boosters and pulls fuel from the main jet, when vacuum drops past the PV value, the PV opens and adds extra fuel to that circuit (like a bigger main jet) it does NOT inject it on it's own.
So, when at idle, the throttle plates are closed, no air is rushing by the boosters, so no main jet fuel is being supplied, and if no main jet fuel is being supplied, even if the PV is open, no fuel goes to the engine
In your case, the PV was likely ruptured, so BEHIND the PV is a vacuum well. When it ruptures, fuel just runs into the engine and will flood like crazy. That undoubtedly was the issue with the flooding, not the PV value and not the PV being open at idle, it just doesn't work that way. So yes it was due to the PV, but not the reason you just stated.
Also, it is very easy to blow a PV, less so with the protection, but it doesn't take much, and if that little ball and spring sticks, or gets hit hard enough, they go away quickly.
One last thing, as a fellow 4x4 owner, be happy you can pull the pan, you wouldn't be able to in a 2WD