My thoughts are that the 88" wheel base is a bit short for a challenge truck, standard 90 length (93"?) or some people go for 100" as they are more stable on hills.
Also if you do a suspension lift your prop angles are probably going to cause a problem.
A V8 can quite good in water, what to watch out for is water in the fuel (that got me twice, as engine running with standard fuel cap under water = water in fuel and engines of any type don't run on water).
Also the other one is ECU under water (but you don't have one), I've never really had a problem with a good coil and 9 and 3 finger rubber gloves (always something else first).