For water crossings in Venezuela with the 1FZE engine, I've seen people run a 1/8" air line from the cab to the distributor. Then another line from the distributor to the air cleaner hose. The air cleaner hose goes from the air filter to the intake manifold. They also seal up the distributor cap really well with silicone. There are some holes below it that need to be plugged. As well.
When the engine is running it creates a vacum that pulls air from the cabin, through the distributor. As long as the cabin is dry, the distributor will be dry too.
The more serious crowd will put a small compressor that can deliver about 20 psi inside the cabin. They will turn it on when they are going to go through deep water. This way the distributor will always have positive pressure.
