I recently bought a '70 pedal assy. off --included support, brake, clutch pedals. The guy who sold it to me said that if I wanted to use the whole thing on my '69 that I would have to drill two new mounting holes in the firewall, because the assy-to-firewall mounts are different widths between 69 and 70.
However, what I think I am going to be able to do is use my existing support and just add in the '70 clutch pedal, as supposedly there is no difference in the pedal support between an automatic and a manual car.
Again, this is only speculation at this point, because I do not yet have all the T5/TKO swap stuff (the next Big Project).