91 Burban Sle Heater Core Replacement

[oxidation]

Hi all,

I've got a classic leak at my heater core. There's green coolant fluid dripping onto the pass side floor mat. I've pulled the glove box door and hot air distribution ducts from the large plastic box that holds the core. When i go to get at the bottom bolts holding the box in place there's these flat headed rivet looking things in where I expect bolts to be and I can't move'em. Is this the typical setup for a 91 suburban? I've attached a pic of the area under the dash. Thanks in advance. Oh yeah, I've got the setup with A/C on the other side of the fire wall, so I'd love to not have to futz around there!

[txab]

I think you'll find 2 nuts on the engine side of the firewall