The steel line on the driver side of the block has two rubber hoses connected to it, a small one going to the throttle body (if your throttle body has a coolant line running underneath) and the other going to the right side conection of the heater core.
On the left side, I can't remember, but it also has two rubber lines, one to the other heater core plug, and then to the other side of the throttle body heater.
Best bet would be to pull the lines off at the fire wall, then use a pipe connector between them to tie them together.
I'm not sure if there would be a problem or not if you didn't allow it to circulate.