Smothing out firewall

Hello, I would like to smooth out the firewall in my 72 Challenger. I have seen where others have covered the existing firewall with another layer of metal. I would do this but am concerned about rust developing between them. What would be the best product to put on the panels before joining them? Is their a better way besides out and replacing the firewall? If anybody has done this could you send me some pictures? Thanks.....Ed

Coat them with weld through primer or butt weld them instead of lapping them.

cut the old one out,as Adam mentionned,use weld thru primer and butt weld,if you end up keeping the old firewall behind the new sheetmetal,spray lots of etching primer in all the holes,once finished and painted spray 3M Rust Fighter

http://store.goferauto.com/083mrufi1834.html

but I would just trim the old wall out

Stefan

It may be possible to leave the existing firewall intack, and attach the new "firewall" to the original firewall with hidden fasteners so it could be removed periodically for cleaning, checking for rust, or any other reason. I remember seeing this done on a car years ago....but I don't recall exactly how the new firewall was attached.

Thanks for the help. I will proceed with caution. Regards.....Ed

Cutting it out is the best way or make sheetmetal patches over the holes you dont want/need.

Cut the whole thing out on my Demon, moved everything under the dash. There was some weight savings as well as the clean look

Old pic..