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).
Yes, there is a difference between the 69 and 70 pedal assemblies. I tried to put my 4 speed 69 manual brake system into my 70 4 speed that had power brakes. I could write a book about how non-bolt in this whole deal was. The big thing is that the 69 pedal assembly mounts under the dash differently than the 70. On a 69, the assembly bolts to the steering colum support from the bottom. On my 70, the assembly rests on the top side of the colum support.(also more difficult to install). The pedal supports also look different. I have some pictures of the two if you are interested in seeing the difference. I also had the stock bushings replaced with roller bushings...well worth the effort and money.