Do i need to use a rubber undercoating or a ceramic paint for high heat on the firewall?

 

Either should be fine as long as long as the surface is prepped /clean.

 

If your firewall is getting hot enough to need high temp ceramic paint you've got bigger problems.

It won't get as hot as you think, normal body paint will work just fine, or undercoating...your choice.

 

I used regular car paint from the parts store that comes in the quart can. I haven't had any kind of trouble with it. Also it is surprisingly tough, I drop wrenches on it on accident all the time and still haven't had a chip. Your firewall won't get that hot to need high heat ceramic paint.

 

Depending if you are just cleaning things up a bit, or doing some serious work. I like using UPOL Ratorliner for the firewall and under body. My header runs within an inch of the upper floor pan and no problems with heat. Don't think rubberized undercoating would handle that. Also tintable.