sealing gaps in air duct M20J

[dominikos]

Doing interior refresh for '78 M20J. The overhead air ducts have gaps between plastic and aluminum. It looks like it was sealed in the past with some black substance. Would anybody be able to recommend a replacement? I assume it needs to be something that can withstand heat and vibration and not be corrosive to aluminum.

For larger gaps, I plan to use duct tape. 

Here is what the air ducts look like right now.

[ArtVandelay]

Im guessing it’s PRC/Proseal stuff, they used it to seal my windows.

[EricJ]

RTV would probably work fine there.    You can also get the foam sealing strips at Home Despot/Lowe's/ACE, etc.

 

[N201MKTurbo]

I redid mine a few years ago. It is just like yours. Mine had some mystery white sealant. I cleaned off all the old sealant and resealed it with tank sealant.