If we get a fair bit of info on this thread, I'll try to consolidate in the first couple of posts.
As to dialectric grease, I put it around the seals of my distributor and both ends of my spark plug wires, although the spark plug end seems to be a tight enough fit that its probably overkill.
A good modification to consider is electric fans. That way, you have the ability to turn the fans off for deep water crossings. That seems to be a big killer with petrol engines, is the fan kicking water up into the rest of the engine compartment shorting out the system.
Of course, never underestimate the power of WD-40 and a couple of paper towels, to dry stuff out after a really deep crossing. I had one crossing a couple of years ago where the water was about 3-4" up the windshield (kind of freaky, because the truck started to float at that point). At the end of the rather long water crossing the truck sputtered a bit and was running rough. A generous amount of WD-40 and a couple of paper towels later, and it was running like new.