The rusty one on the water pump is for the heater core, the one on the intake is not. It's hose should make a quick u-turn and go down and to the left (passenger side), don't remember where it ends up but it hooks to something about 5 inches down behind the fan belt.
The other hookup for the heater core is on the passenger side of the intake next to the ignition control module mount. Let me know if you need a pic.

Edit: just looked again and it looks like you already have the return hose hooked up...

 

the one by the e.g.r valve hooks to the water pump as well closer to the alternator though