Yes, I cheated, but you need to do some math AND use a transmission line pressure gauge (from the pressure test port on the side of the transmission), to make sure you set the cable with the right amount of travel and proper pressure rise.
Mine is set such that with just a small amount of pedal move the pressure starts rising, and with the pedal on the floor there is a 1/16-1/8" of travel left in the cable, as in put the pedal to the floor and pull the cable with your hand and see that it pulls out just a tad more. My Firebird has an arched shaped pedal rod under the dash so there is some funky geometry going on, a straight rod would be easier to find a sweet spot with.
I simply took a TV cable bracket, cut it, drilled a single hole in it for a sheet metal screw to pass through to secure it to the firewall, added a strip of metal to the bottom to angle it downwards some in my case so it doesn't pull at an awkward angle under the dash. I used a cable crimp (5/16th?) with a welded on tab for the cable's clip.
The pedal side.
The engine side.
