Throttle Cable

I am not to sure I am posting this in the right section, but since this car is a slant six I figured I would start here.

The car is my 68 Dart with the slant six. It originally had the single barrel holley on it that never really ran right. Well about a year or so ago I found a place that had a NOS carter BBS that I installed. I dont have the numbers with me but I think it was for either a 67 or 68 170 slant six. Though it is a little small Slant Six Dan said it would still be my best bet. The car has never ran smoother.

So after doing some winter maintenance and doing my wake up from hibernation ride I noticed a lack of umph while going up a steep hill. So I had my fiancé sit in the car while it was shut off and floor the accelerator and noticed the throttle blades were not fully opening while looking down the carb.

When I tried to adjust the throttle cable to allow the accelerator to open the throttle blades fully I noticed the cable was already fully taut. So it is almost like the current throttle cable in the car doesnt have enough travel to let the throttle blades go from fully closed to wide open.

Was there a different throttle cable between BBS and holley equipped cars? Is there another cable I could use that would not interfere the fully closed/fully open positions of the throttle blades?

Though in normal leisure driving this could be over looked, in my current location it can not. This car gets driven during rush hour in Pittsburgh. Which has terribly designed roads/highways all over hills and mountains. I need all the power I have to safely keep up and merge with traffic.

thanks