Who is the best supplier for complete floors, braces and trunk pans, and what companies to stay clear of?

I'd like to hear from anyone that's installed a set of firewall to frame braces on their '68-'72. I believe the Camaro guys call these "firewall G-braces". The new bb motor had about 3/4" vertical movement. (When putting the car on a lift, it was first noticed.) I have a tight fit of the...