First version is done! I decided to go with more of a hand throttle for now because that's what I had the parts for lying around. I have friction shifters coming to make it more of a high idle device.
I used a few blocks (pulleys) that I had from my sailboat and an old mountain bike brake lever and cable assembly. I welded up a bracket that screws into the firewall that holds the bike cable and the bottom block. On the pedal I bolted an angle bracket on with a pulley attached. I used small no stretch line for the intricate part and steel cable for the rest.
It works perfectly. I can loosen the adjusting barrel on the bike brake just like you would do to adjust your brakes to increase the idle. I can also use it as a hand throttle for hill starts and such. It is a bit of a learning curve to drive with but easy once you practice.
When the pedal is used normally the pulleys just pass right by each other and have no effect on the operation of anything.
Let me know what you think!