No heater, can these be plugged?

[Volksnut]

It will be a while until I add heat and air, can I plug these or does it need a bypass hose for coolant flow?

 

[RemCharger]

Plugged is fine.

 

[steve340]

I think the internal coolant bypass hole is supposed to be drilled under the thermostat hole.
Better check it is there?
I remember someone else posting they had bought a replacement cover and it was not there.

 

[Volksnut]

It's there