The problem with going "hood deep" is the fan. If you even get into 2' of water, the bottom of the rad fan will be under/in water. It will then "spray" the water all over your engine.
Assuming your engine is in PERFECT order, it should survive this. However, if you have a bad plug wire, loose plug wire, bad distribuor cap or rotor, or ANY KIND of non-weatherproofed electrical connection... BAM instant Electrical short.
If you look under the hood, you'll notice that the air intake opening has it's bottom LOWER that the bottom of the hood. If you go "hood deep", you'll be sucking water into the intake system. VERY BAD. Unless you install an intake "snorkel" and then test it with soapy water to verify you have no air leaks... Stick to 2' of water or less.
If/When you install an axle/diff/crankcase breather extension kit, route it to the snorkle, or some other "high" point on the vehicle.
Properly modified, you can drive into water OVER hood high, but unless you want to go to some extremes with modifications (and very few do), I reccomend you stick to the "wading pool" depths.