[Doug Tatham]

The A/C evaporator box and heater core box have panels that direct flow of air. They are made of metal and covered with foam rubber. I used window self adhesive insulation and protable A/C unit filters to fix mine.
You have to remove the instrument panel, instrument cluster, and dashboard to get to the cores. You have to drain the coolant to get before removing the heater core as well as have the A/C system discharged. The heater core and evaporator boxes have bolts on the engine side of the firewall that will have to be removed. You should replace the drier on the A/C after opening the system up. Expect to put in a very full day.