wow, what year was it that you bought/sold it?
I have a similar issue with my 65 fastback, my knee is right there on the door panel. I adjusted the stopper and pedal travel and it is better, but I am only 6'2 and have the seat all the way back. It makes me wonder how Carroll Shelby even got in one to take a spin around the track, I think he was at least 6'4. Mark Donahue and the other drivers who drove the 65 must have been like 5'8, any taller and shifting is not really as fluid. Now the 65 is a bit smaller car, the 69 on the other hand appears bigger (at least longer) than the 69 camaro, so I am surprised it was still an issue. Were guys that much shorter int he 60's?
In my 69 camaro I have the seat all the way back, but the car just fits me better, I don't have any issues with my knee when real easing the clutch.