I have a pretty extensive discussion of this here on the first page of our assembly manual. We use holes and the rubber grommets MSD supplies.
I would be very, very leary of a stick bond type fastener. The glue (no matter what it is) will soften as the firewall can become extremely hot. I don't think it would last long.
David
http://clubcobra.com/forums/showthread.php?t=80230