I guess I should have mentioned the braces!  I have two upper braces, one on either side of the radio stack.  The other runs from the lower right of the radio stack to the firewall brace.  They are all 3/4" angle aluminum.  If you run braces on the top to the firewall flange they will interfere with the defroster, so you need to attach some mounting bracket a couple inches below the top of the firewall.

 

Photos attached.

 

Mike