What happened to the dual spring that came in the throttle return kit? Here is how the setup should look. I'd recommend using a stock cable with the crimped on ferrule. That way you have something solid to clamp to.

this is the return spring set-up i have...dual springs (came with 4, a heavy set and a light set)...on longer trips, even the light springs are a pain in the foot/ankle, so normally i just have one on.

the turquoise set-up above is missing the valley pan hold-downs

Slant Six cable is long enough or get one from a pickup truck. Some part numbers are still available from your local Dodge dealer or try Mancini Racing. There are reproduction throttle cables available also.

From another post so you have an idea of how it was designed to be installed.

Lefty had it

What original slant 6 cables are AndyF and DirectSubjection referring to? DirectSubjection mentions his original cable worked for him but what year and bodytype mopar does he have?

Oh sorry - 70 Duster but I believe any cable for the version of your car originally equipped with a slant six would provide the length needed.