As you have likely read, hoppers have their downsides, especially when it’s well below freezing, in unattended use, or when there’s lots of minerals in the water. Another use for the cooling manifold is cooling with a barrel or radiator, plenty of info on the utterpower cd.
The plate shown if fitted with thermostat housing and cold water return, hundreds of engines use this system.
Just two complete units left, thermostat uses NAPA #283 or similar. Laser cut, welded in heavy one inch flange receives standard one inch pipe or hose nipple. Thermostat housing CNC machined. $129.95 with shipping in USA 50 states.
Engines larger typically use a different pattern, engines smaller use a different plate as well.