What is the correct throttle cable length for a 68 383 w/ 4bbl

[Corellian Corvette]

My existing throttle cable is too short and won't allow me to place the cable behind the bracket and still allow the throttle to close all the way.

I ordered a new one from the Paddock, and it arrived and it's 21in. That seems like it's going to be too short.

Is that the correct length before I go ahead and install it? I've heard there are 24in and 26in cables.

Thanks!