[Jim727]

As I recall, the evaporator core is sealed around the perimeter. I pulled mine about 6 months ago to replace it with a Griffiths serpentine-type core (very nice part, btw) and anything that looked like it used to be foam was quite deteriorated. The Griffiths core had a more substantial piece of rubber around the perimeter and another harder plastic gasket that sat on the shoulder of the evaporator box between the box and the core. Logically, air needs to go through the core, not around it, to be cooled. Any good hvac shop should be able to recommend a sealing material.

"While you're in there" you should probably also check the foam seal between the footwell warm air intake and the smuggler box sheet metal. That was also deteriorated in my car.

Also, make sure you don't kink the temperature sensor tube while you're moving that around. The sensor tube fits into a brass receiver tube that goes through the evaporator box cover and into the evaporator core. As I understand it, the receiver tube ideally should contact only the core's fins, not any of the freon tubes. Someone more a/c knowledgeable might have better info on this.