When I bought the yellow truck (79 F350 460 C6) it had a 4160 Holley, a 3/4" spacer and an Offy manifold. The kickdown lever wasn't even close to connecting.

I pulled the Offy, and the spacer, and installed a Performer and a new 4160 carb. The kickdown is closer, but still not quite right.

At rest, the kickdown pulls the throttle open and the idle is too high. When forced onto the shaft, the kickdown travel doesn't allow the carb to open to full throttle.

I tried the Holley kickdown extension, but that doesn't work either. At rest, the kickdown needs about a quarter inch more, and (following the accelerator arc) needs about an inch.

Any ideas (other than downshifting from the column) are greatly appreciated