I have a new core for my 76 F150. The old core had foam compressed on both sides, but it has completely disintigrated. Anyone have suggestions for what to replace it with? I guess it has to be tough and heat resistant.

I assume the foam is to protect the core from rubbing against the heater box sides...

 

Dense pipe insulation should do the trick. It should hold up to the temperatures of the coolant just fine.

 

Pikachu is right on the money, and 100% correct. in fact, the pipe foam insulation will do a better job than the factory stuff, and last longer as well.

 

Sounds like a great idea! Thanks!