its not a /6 vs V8 thing, its an early vs late thing, sometime around 1970 they changed the leverage ratio to decrease pedal effort due to complaints from people saying it was to hard (yea /6 and V8 use different Z-bar)
See thats the thing...I've run, with the same linkage for both, the 67's and the horizontal lined pedal padded 72'ish and up pedals, with no feel difference.
Thats why, along with never hearing about the ratio change, I'm having trouble with this explanation, I could be wrong...but i need to see it to believe it.
