55.2-59 Firewall Pad

[57FleetsideC4]

Hi All, On the 57 I am doing I am starting to weld in the holes in the firewall I don't need. There is a series of 3/8" holes that look like for the firewall pad I am guessing. The question is do most use some sort of Fat Mat/Dynamat type material in that area or the stock firewall pad? I was thinking of laying down fat mat throughout the whole cab to quiet it down. Thanks Steve