Will not KICKDOWN (340 6 PAK, 727)

The spring he has on the front of the throttle linkage is definitely much larger/stouter than needed but it's only purpose is to pull the throttle pressure linkage back to idle so it's oversize won't hurt anything other than maybe make the accelerator pedal harder to push down. And note that some linkage setups do have it installed on the rear but it's function is the same.

KIII check to make sure that when you floor the throttle from inside the car it's going wide open at the carbs. If it is adjust the throttle pressure linkage so that it is pushed all the way back at wide open throttle. If it's not going all the way back (or real close to all the way) it won't kick down. If you do find it's not going all the way back and adjust it so it does test drive it and see if it shifts like you like it. You may find it hangs in each gear too long. If it does that back it off 1/2 turn at a time until you get it where you like it. If in your inspection you find the throttle pressure linkage is going all the way back at wide open throttle you have a problem in the valve body.

BTW: for clarification the throttle pressure linkage I refer too is what people normally call the kickdown linkage. Throttle pressure linkage is the factory terminology. And it adjusts the same whether it's a 2 barrel or 4 barrel or 6 pack.