thanks guys,
unfortunately the 78 pedal and frame are slightly different to the '79. The 79 pedal has a longer pivot that goes through the frame and "I think" through the tension arm as well, and then though an extra bracket. I'm not sure though because it was apart when I got it and that's where I'm getting confused.
Plus there's an extra hole in my frame under the brake pedal that I can't find a use for
I'm thinking I may have to post a pic.