TCP has an ultra clean set up for the 64/66
If you go to their web site they have pictures. I especially like the way the rear portion welds on, then when you mount the cross brace, you are not drilling and bolting through the frame, like you are on the coupe and fastback. Look closely at the rear plates on the connectors.
It fits fairly tight to the floor pans and is made of tubular stock. If I was going to copy anything, this would make a great base to work from.
Scott