kickdown cable making problem

I bought a 40 Plymouth project car with a 340 and 727 trans. Got the car driving and took it for a 1 mile ride. The trans worked fine. As I finished the car I put a Lokar kickdown cable on it. Here's the problem; Without the cable the trans works fine. With the cable it won't shift to 3rd gear. Kickdown works fine from 2nd to first. I've followed the 1to1 cable placement between the carb and linkage arm. I've adjusted it using the gas pedal floored instead of WOT at the carb. I changed fluid and filter. .........I saw someone on this forum recommend a small return spring on the arm and adjust the cable slightly to change shift points. I'm giving that a try next. Does anyone else have an idea I can try? I just want to try every suggestion on a day I can dedicate to this