24" or 36" 318 throttle cable?

I really think that you are over thinking this one. No need to disconnect the pedal assembly from the firewall at all?!? If the hole where the cable passes through the firewall is too big (did someone drill it previously?), you could always get some fender washers from the hardware store. The cable feeds through the hole in the firewall and you thread the nut on the inside. It really was about a thirty minute job.

Here's a pic I just snapped. Yours may be different. Man, it's cold and dark in my garage at 6am.