That should work but even a non WP distributor should work unless flooded with water. You might want to try sealing around all the spark plug wires and terminals with silicon grease.
The Fording system on a M38A1 is a LOT more than a snorkel and taller exhaust pipe! It vents the crankcase, the fuel tank, the transmission and transfer case, valve cover and the brake system IIRC. It supplies clean filtered air to all of those and also a partial vacuum to the to pull fresh air through several of them. The Fording system's air supply is taken off in of the air intake in front of the carburator so everything gets it's air from the snorkel and they won't flood until it does. There's a lot of plumbing involved!
Does your's still have the water proof generator and the water tight voltage regulator? You need those too if you're going to take it into deep water.