Ok take a look at this. I had some walnut 1 1/4" thick so I made the blocks out of that. 4 bolts go through from back of the firewall through the aluminum plate. I had to mount 2 of the standoffs inward slightly due to clearance but kept them as close to the solid blocks as I could. Nothing epoxied yet but will epoxy the blocks to the firewall. Didn't get pics of the back side of the firewall but I used heavy fender washers at the mounting points.