I have run my V8 thru rivers, and miles of floods in Oz . I have the head of the coil in a lexan box with silicon seals where the wires go in and out , this fixes the biggest weak point , the top of the coil. The export models sent to OZ were even worse than UK set up as the coil was mounted down low on side of radiator , at least mine (UK model) was originally mounted high on top of inside wing. I also made lexan box and mounted ign amp inside . The leads need to be in good condition, so they make good seal on plugs and distibutor cap, I also ran bead of RTV round cap joint. I drilled body of dizzy, not cap and fitted breather tube, same with both lexan boxes, these breathers are T off air intake snorkel. I tested with pressure washer, and never missed a beat i then was confident enough to cross creeks etc , you can tell the water was deep coz my off road trailer actually floated behind the landy, the wading plug on bell housing only really needs to be in if you are going to try and change gear when in water, as water will get on flywheel face when you depress clutch pedal and give massive clutch slip, think what your drum brakes are like after going thru water. If your bell housing is not sealed well, having the drain plug in can actually prolong slip probs as the water that gets in via other leaks wont drain out till you remove the plug.
Best advice tho is try and avoid deep water unless it cant be avoided, as they were not designed as submarines, and you need to check all fluids as soon as poss after wading , as a little water can do a lot of damage . JMHO
