There was a reasonable head of water with the radiator cooled engines, but as has already been mentioned, these were not intended or used with any pressure in the system, even the radiators were vented to prevent build-up of pressure.
A later head is mechanically compatible as far as I can see from the changed number listing, but as the injector itself may not be compatible with the later head, you may have a problem if you cannot source a head etc where you are located.
Tank or hopper cooling works fine as the latent heat of evaporation of water takes an enormous quantity of heat out of the engine with not much water loss, which is why it was so popular.
Don't try and take out too much heat, these are not engines that tolerate low temperature running.
Peter