Where can I get a new seal for my non a/c heater core?

None of the regular autoparts stores carry it.

It's for a 72 Malibu.

You may have to get the heater box seal kit, which includes all the seals needed for the fan, core cover under the hood, housing under the dash, the seal that covers the inlet/outlet and other seals internal to the inside box. Check any of the usual suppliers for the kit, Ground Up, Year One, Hinshaws, they all should have it. I just put mine in.
John

Does the heater box seal kit have the white rubber grommets that are internal to the inner heater box? I have a 1970 Chevelle (without air) and the inner half of the heater box has 2 white seals which seal air flow to a section of the box.
They look like they would be difficult to replace. Has anyone replaced these before?? Are they in the seal kit?

Thanks
Tim

I'm usually hanging out in the Transmission section of this list.