I used a bluebird series 1/2 setup including the whole pedal assembly, master and slave (for a nissan box). It works beautifully and parts are everywhere. I deleted the old cable pedal. You know with this system it all works in together and I have had no problems. I also used a thin plate on the other side of the firewall to the pedal to add stiffness. It was cheap easy and was in and working within a few hours. just install the new pedal assembly anywhere you want in a position where you feel comfortable changing.

edit... just a thought you know with this setup too you have the right leverage geometry to push the pedal and the master. This is where I think you have it skewed on your setup making the pedal really hard.