The most important thing when installing the w/pump AND the LOWER thermostat housing IS :
just make SURE that the water pump mounting surfaces are Clean & no - burrs . Do the same thing mounting that lower thermostat housing .
Then, tighten the bolts down even ……. those mounting " EARS " can and will break - off. the lower thermos housing should be either Alumn. or Cast Iron.
Just make sure each surface matches up ' square - or - flush" . That also goes for installing the top thermostat cover ……. you can break them easy.
Make sure your "Thermostat" is sitting in the "Groove" .. you can see that . Just go steady and NOT Too tight.
Make 'em tight , and check them after you fill your system …. You can always go back & snug-them down more.
The torque spec 's --- the water pump may show some 'spec's ……. It's not very much ; just make everything match up smoothly .
Look at the gaskets -- just get them straight -- it will work .