If you are adding the strap support from a 68-76 due to 67's do not have the dual straps the mount slips through the floor. After cutting the slots slip it though an spot or tack weld it in place then seam seal it.
The hard part is reinforcing the cross member for the other end of the straps. I wonder how other folks do that. I am thinking about opening a window in the floor and tacking in the reinforcement. Its been a while since I have visited the situation.
