I am using a brand new 4 bolt iron factory replacement for the manual disk brakes. I got it for free from a buddy. If RMS carried them I would buy one from Bill. Seeing how I don't see one in his store I'll make my own. My question is what is the thickness of the aluminum stock? I would think it would be at least 3/4" to offset over the raised rib area in the firewall to the drivers side of the master cylinder.