Scott, Was your car originally a V8 car? It it wasn't, and you are using a six cylinder pedal assembly with a throttle cable, you will not have the provision to mount the throttle arm to the pedal assembly and you will have to purchase a V8 pedal assembly. The mounting bracket for the pedal assembly on the firewall is the same for both, but the V8 has a extra 1-2 inches of rod to mount the throttle arm, and the six cylinder is just 'C' clipped after coming through the firewall.
Mark is right, refer to the assembly manual a.k.a. "The Bible"