the top center fitting plumbs to the thermostate fitting

and on my car this other  fitting is plumbed to a remote water tank 

to aid in cooling ,which is then plumbed back to the radiator.

I would like to remove that system with a cleaner recirculating metal can system

next to the radiator, but am not sure what to do about this water fitting at the top of the pump,

can it be blocked off ?

thanks in advance , Carson

      Up north that fitting is used for a heater hose.

Frank/Rebop

Bristol, In ( by Elkhart)