Also, consider that a snorkel is not always enough.
Completely agree; most people think a snokel makes the Jeep a submarine, but you still got to worry about ignition and electronics. It does reduce the risk of blowing out the engine due to hydro lock, though, and improves your ods of getting through a river like the one in the video (which is actually a shot from Panama; if I were to cross it, I would feel much safer with a snorkel than doing it like the guy does in the vid!):
http://www.youtube.com/v/kZ45DuXsOFE&hl=en&fs=1This is another sample, this one is '94 YJ (same body and color as mine, but this is a Sahara edition with the 4.0L) from a friend of mine with the safari snorkel (and yes, he's using 2WD because he bet another guy he could get through the river without 4WD; not a smart bet, if you ask me, but he won it).
http://www.youtube.com/v/gUCdjRoFt5E&hl=en&fs=1Regarding the dash idea, I rather have the intake up higher than the dash; if you are moving forward, the dash is fine, but if you get stuck, the water level could theoretically rise and flood the engine. It IS a better position than stock, though, as the nose dips into the water during the approach, and this setup would avoid that, and also while moving forward, the cabin would flood much slower than the engine compartmet, giving you time to shut the engine off if you do get stuck, but I still think having the intake as high as the roof is better (although if you DO flood the cabin all the way up to the dash, you got other things to worry about as well!).