The 6.7 Powerstroke runs an air/water charge air cooler straight from the factory. It is comparatively small. They do run a separate low temp cooling system for it.
I didn't know how much water u would have to run in it, meaning weight. But if the cooler is smaller might make up for it. Is the 6.4 unit run off of coolant I would imagine? I would cycle some ice water through that baby. But that might not be practical for street use. Plus buying an air to water intercooler would not be cost effective for me but if I made one it would be different.