I have a cobra kit car and previous owner used donor accelerator cable and bracket from 74 ford. It was ugly and didnt allow carb to open to full throttle. I replaced with a Lokar cable. Now the peddle is very difficult to depress. If I take the return spring off peddle does work freely. I removed the springs I bought from autozone and I am using a spring from a lawn mower which is pretty flimsy (but allows peddle to work easier) , doesnt pull the carb to initial setting (engine rpms to high). currently just have a chrome bracket that is held in pace by intake bolt and is just a post to connect the spring. I have adjusted the bracket to have the spring taught but still no good. Should I purchase a return spring bracket that attaches to the carb? shaped like a c ..........

 

I think that would work...you also want a dual spring setup...usually one smaller spring is located in the bore hole of the larger main spring.

 

If you want to play with springs, try McMaster Carr. https://www.mcmaster.com/#springs/=1d2etry
You can get alsorts of ends, diameters, length and force and cheap so you can try several until you get what you want.. Try the corrosion resistant with special ends. some you can configure your own ends. They are pretty fast delivery. Where I am, if Iorder almost anything in their catalog by noon, I have them by 5. Don't know how they do that.
Good luck