Pulled the heater box and replacing the evaporator and heater core. Noticed all the foam around the vents and blend doors are trashed. Turns to dust when touched. Are there replacements for these or can I use weather stripping from Lowes and piece it around.

 

No replacements that I know of. One member here used something (I think his name is Atomic and he might chime in). I (and the dealer when I worked there) used closed cell foam. I bought mine from Lowe's, just have to trim it

 

I recently rebuilt my heater box.
I used adhesive backed closed cell foam (1/2”x1/4” door seal) from HD.
I just cut strips to go around the perimeter of the doors.
Worked great.

 

You were the one I was talking about