Heater core with A/C question

[718jwh]

I am assembling my heater box with A/C and am wondering if there is any foam strips that go on the heater core or the box in the area where the core touches the box I don't remember if there was anything when I disassembled the old one. I am using a new aluminum heater core and was thinking there should be something between the aluminum core and metal piece it rest on in the box

Thanks
John