Semi Urgent....Radiator/Heater Plug?

All, decided to fluid-up my 2A today, and all of a sudden while filling up the radiator, splish splash! Oh $!
On the inlet/outlet thing on the flat head, on the head, there seems to be an extra port, for maybe a heater? Well it's comign right out of there and I just have it draining back into the jug.
Sooooo....
What can I do to plug that thing? Is there like a rubber cap that I can hose clamp in there? Or will I Just have to use the finger of a thick rubber cleaning glove for now?
TIA

 

you should be able to get a brass plug from your FLAPS to fit in there. mine is open/in use because of the Summit heater i have but you'll need to plug it if you arent going to use it.

u know what, i might have the old plug somewhere... take a pic of the spot you are talking about... if its the same as the one i took out for my heater, i'll send it to you

 

Steve FTW! I pulled the old one off the old water pump (the barb or nipple, w/e) and I need another Male-Male fitting to go the 90 and out, but, as soon as thats on, I should have no leaks.

Everything leaked tonight though, I get to drain everything tomorrow to get the anti freeze out of it
One stream from an exhaust stud that wasn't good enough (thanks for the wrong part Carl) but fixed it with just using a bolt, the other was up top where the heater was, this thread purpose. Right now I have it shut off with a latex glove and a zip tie. Oil-no leaks, tranny trans case, AFAIK no leaks. It'll need like 5 bottles for the tranny, trans case, OD, PTO.
Thanks