As far as I know, this is the only galvanized steel in the kit. I guess aluminum doesn't have the heat rating and rigidity needed in this area. I tried a couple of different ways, but it worked best for me to clecoe each firewall half (it's split vertically) into the sides, then fit them together in the overlap groove and begin clecoeing all the support angles and channels. The firewall fits very snugly, in fact, the sides are formed around the firewall curve so I found this approach to be the only way I could get to work.
It is absolutey incredible to see how stiff the firewall gets when all the rivets are pulled. Of course, that's a good thing if you are going to hang an engine off of it!
